First of all, Nigel Farage has literally made a career out of denigrating the European Union. No matter what actions the EU takes, Farage will continue to insult it. That's what he does.
The EU and UK are currently negotiating the terms of Brexit. The interests of their respective governments are not exactly the same; that's why a negotiation is needed in the first place. However, the two sides in this negotiation are nowhere near equal in size and economic leverage:
- Population: EU27 445 million; UK 65.6 million.
- GDP: EU27 US$13.5 trillion; UK US$2.6 trillion.
- Trade: 44% of UK exports go to the EU; at most 18% of EU exports are to the UK.
- Industry: Key UK industries, such as car manufacture, pharmaceuticals, and financial services, are heavily dependent on agreements with the EU; and they may leave the UK if similar agreements are not in place after Brexit.
So the EU is able to insist on certain conditions, such as the sequencing of negotiation topics, and there is very little the UK can do to stop it. Whether this constitutes "bullying" is a matter of opinion.
However, it is worth noting that the governments of the EU27 are democratically elected, and have a responsibility to protect the interests of their people as they perceive them. They will not simply give the UK everything it wants, and would be failing in their duties if they did so. Farage can call it bullying if he so wishes, but this is how international negotiations work.