Farage is correct about one thing. If the wealthiest in America all went full-on far right and bought a controlling interest in the major financial institutions, they could make life very difficult indeed for their political enemies in America. It's not like it's possible to get sensible regulation through Congress, right now.
Whether Barclays, or any bank, wants to do business with Farage is fairly immaterial. Banks do that to big clients, when they decide they're not worth the attached risks. The banks that don't get the snot sued out of them for doing business with people like Jeffrey Epstein.
It's easy to forget that someone like Farage can come attached to hundreds of millions of dollars or pounds in legal exposure, and he's glossing that over.