What law?
We're in the area were private businesses are running essential services, banking in this case, so they can make their own rules up depending on whatever political grounds they want. They don't have to give a reason.
That is the problem. When we move to a cashless society are you happy that a bank can decide what you can or can't purchase?
If we get a far right government in and the country swings back to victorian morals. Eventually anyone promoting anything outside of religious values would be seen as a disruptive person. They go on to social media and see you've wrote verboten things. Then when you go to your banking app you'll get the message 'Sorry, we have no record of this account'.
That is where we're heading. People like Farage and others are the easy targets. The canary in the coal mine. It's to get all the people who don't like Farage, and the people who don't care, to accept it as the new reality, as surely it'll never happen to them...
Any person expressing anti government views will be susceptible to this at some point, no matter what your politics is.
As said before it's happened to plenty of people, the difference is that they often try to find out what the issue is rather than moan about persecution.