They must have liked him at some point, to have accepted him as a customer in the first place.
I am trying not to take sides in this. Plainly the bank acted poorly, but they aren't just any old bank: although I agree that you shouldn't discriminate against people because of their viers, well, Coutts are a pretty discriminating outfit to start with, and if they decided they were finally fed up with Mr Farage, a high-profile and controversial figure, while I don't condone it I can understand it.
I'd be more worried about Joe Bloggs having their account closed for no reason by a High Street bank.