Both "sides" do not support killing and violence.
Your view of NI politics is really, really simplistic and I've explained the issues below.
Violence and killing and the actions of extremists who are, as in most cases of terrorism, a tiny, tiny minority. They make headlines, but they're not what "everyone" thinks.
just like a significant fraction of Northern Ireland wants to leave, and both are willing to kill the other faction to further their goals
Again you're confusing the (possible, but not happening) actions of extremists (a minute part of the population) with the way "both sides" actually think and behave. They argue, like anywhere else.
Since the GFA there has been relatively little civil unrest on a large scale. It's arguably no more dangerous than the rest of the UK.
Roughly half of Britain didn't like Brexit, but if there've been terrorist attacks by Remainers on Brexiteers (or by Brexiteers on Remainers), I've not read about them.
I wonder how many drunken arguments over Brexit have escalated violent assaults and gang-on-gang fights ? There are no figures I know of, but I bet there's been quite a bit of violence all over the UK.
Well I don't expect extreme violence, but it's not impossible as a later development. For now BrExit has not actually happened. No one knows the consequences (and the UK government never thought this through). There will no no social unrest, much less violence, until there are reasons to drive it. I think talk of "riots in the streets" is really rather silly. Elections, yes. Short, unhappy periods of government after government that fall one after another quickly. Economic problems, yes, for sure. But riots ? A football result can cause a riot, but probably not Brexit.
Also note that within the UK, the move to independence for Wales and Scotland was largely happening anyway. Within England, there are social divisions (rich and poor, maybe racial) but no real political divides likely to cause mass riots and terrorism.
The UK already has terrorism, BTW. It already has terrorists who "soak up" the disaffected in society and turn from them problems to disasters for everyone. All societies are like this.
Roughly half of Scotland voted to leave the UK, but if either side have attacked the other, I've also not heard about them.
Another strange view that political disagreements result in violence. Actually less than half of Scotland voted to leave the EU, like NI, but they got dragged along in the "have to leave" result.
Roughly half of the US votes for the party that does not win in every presidential election, but they don't attack each other.
As in most countries, most people are largely apathetic about political matters that are not huge and do not affect them on an everyday basis.
US elections, like so many democratic elections, are a wealthy elite fighting it out for power. It frankly has little to do with the man in the street.
The Irish (!) same-sex marriage referendum in 2015 also didn't result in violence.
I am Irish (!) and I don't know what led you to think the same-sex marriage was ever going to lead to violence. We've been happily operating a very peaceful democracy (with fewer riots than the UK) since the Irish state stabilized after the civil war (1920's).
Ireland (the Republic) is a very peaceful country.
both are willing to kill the other faction to further their goals.
This is simply incorrect.
From your other question it is clear you have a very, very over-simplistic view of the world and the people in it.
You confuse the actions of minorities with the beliefs of the majority. This is wrong.
Here's the way it was in NI during and before the Troubles :
- The population was roughly equally split by religious social groupings.
- Due to rigging of election boundaries, the Protestant grouping maintained an absolute political control of the province.
- During the sixties, a time of social revolution everywhere in the Western world, protests (peaceful) broke out seeking these perceived injustices to be corrected.
- Troops were brought from the UK to stabilize unrest, but contrary to what you may think, these were initially very welcome by the Nationalist/Catholic community. Note that the NI police service at the time was viewed as a Protestant/Unionist dominated body and seen as biased in matters of social injustice. SO UK intervention was actually welcomed at the time (by most people).
- Like similar events in most countries, the vast majority of people just wanted to get on with their lives. They weren't politically neutral - they had opinions - but they wanted things dealt with (ideally) without the unrest.
- The use of troops went badly and there were significant incidents where they over-reacted and created a very hostile relationship with the Nationalist/Catholic community. The troops rapidly became part of the problem and not part of the solution.
- Extremists on both side (a tiny, tiny minority of both communities) became terrorists. This happens everywhere and is an inevitable consequence of failing to address social issues with politics (and it can happen without any mainstream issue at all).
- Again, over-reaction by government and local policing (who were suddenly expected to be both police and army - something they were not trained for), escalated matters on both sides.
- Extremist politicians on both sides exploited the fears of the masses on both sides, who had significant historical reasons to distrust each other anyway. It didn't take much to make the politics of NI completely them-and-us with little or no middle ground.
- Deaths (civilian) and atrocities (on both sides) hardened a new generation who grew up in this mess into people and they became firebrands and, in a small number of cases, extremists.
- The normal criminal activity in any society (about 1% of the population) became mixed up in the extremist groups on both sides. This made it much harder to avoid getting involved in extremism than it would otherwise have been.
- The UK and Ireland both independently joined the EU.
- Political activity developed a peace process and social pressure for change.
- The Good Friday Agreement (a formal legal agreement between governments and social groups) led to the end of violent extremism. Hard work has kept that peace.
- BrExit is not in and of itself a real issue for either side.
- But power sharing (as required by the GFA) has been stalled as both sides cannot agree a way to form a government. Both the UK and Irish governments, as well as EU and US politicians, have encouraged this and tried to make power sharing restart, but it has not happened.
- BrExit came along and a weak Conservative government took support from the DUP party in NI. But the DUP have an agenda historically attached to their largely protestant/unionist support base. They have attempted (explicitly) to use BrExit to get rid of the GFA and to harden the UK's attachment to NI. They are effectively blackmailing PM May's Government.
- This leads back to the days before the Troubles, where one side (the same side !) had political dominance and tried to exploit it for their own benefit. That, at the minimum, is how the Nationalist/Catholic side sees it.
So this dangerous problem of exactly what political status NI has within the UK and EU is quite plausibly likely to restart the Troubles. But restarting the Troubles does not necessarily mean restarting extreme violence and terrorism. Mostly the troubles were driven (and started by) social injustice, poverty, the need for electoral reform.
So maybe more political problems, more strikes for political reasons, maybe the odd riot, stone throwing, that kind of thing. Terrorist extremism on either side is an unknown. A scary unknown, but an unknown.
The peace in NI rests on a perception of social justice which requires the GFA, the EU and both the UK and Irish governments to maintain it. It would not be perceived as "fair" by both sides without this awkward balance of influences.