TLDR: They don't and they mostly don't have to.
Let's change subject for a second. Imagine, in a news conference, DeSantis being asked
"How does coercing Disney Corporation fit with Republicans' pro-business, pro-economy stance?"
"You are right, I can't justify it and it doesn't. My office will call that off".
Do you really expect that to happen? No, it won't, you'll instead more likely get something like:
"Floridans are sick and tired of being indoctrinated by woke corporations. You there, next question?."
Let's break that down.
A politician will dodge the question or answer past it.
They will then move to a different question. You can't realistically expect some form of structured and controlled "But you didn't answer my question!" format. Not least because typically at a press conference there are many journalists asking questions and thus good reasons not to let one monopolize microphone time.
Depending on the country, the journalist asking too hard questions may get frozen out. IIRC that is what Trump tried to do at least one once with the White House conferences. Just because Trump was too clumsy about it doesn't mean it doesn't work when done more carefully, especially when it concerns foreign relations, rather than pressuring internal politics.
There are exceptions, circumstances where hard questions can be drilled to a politician on repeat. Congressional hearings, WTO hearings, presidential debates, etc... And it that case, dodge tactics are much harder to apply. But this isn't the context of your cited news conference. In most cases, the more "technical and formal" the Q&A format, the more limited the audience: "if can't be a soundbite, it ain't news".
To a large extent, a politician in these circumstances doesn't really have convince anyone: at most they need to avoid contradicting themselves and looking dishonest. The audience will be divided in three camps: sympathizers, opponents and undecideds. The first two won't change their beliefs and the third group probably won't and/or represents a limited risk, both in terms of actually being swayed and in their influence.
In the 80s, the US long managed to limit Japanese car imports? Was it "fair" and free market? Ummm, not really, but that didn't stop it from happening. Most of the time, there are no hard penalties to stop countries from misbehaving, but there is of course no guarantee the targeted country won't push back with its own economic coercion.
Back to US+pals vs China, in this instance:
Lithuania got all sorts of economic pushback due to it supporting Taiwan. That was standard China reaction to criticism of its domestic/foreign policy. Could have been the same on Tibet. Or Uyghurs. Would it fly at a WTO hearing? Probably not. Keeping out Lithuanian beer has no real economic rationale.
The US and a number of countries have shut off Chinese access to EUV equipment. If that goes to WTO, that would probably cruise by due to national security exception clauses.
In matters of trade, in many cases it doesn't really matter who is right or who is wrong, it only really matters how much leverage each party has and what enforcement mechanisms exist to bring back the "wrong" side into line.
* Well, as the West is slowly realizing, it still has some way to go before its PR is fully convincing to non-aligned countries, even given such a black and white moral context as Russia's aggression against Ukraine. So, too much cynicism, as implied by my answer, can backfire. You can't just sail by when trying to influence the undecideds, you need to establish a real rapport with them.