Perma-Banned from game for offsite comment - is that legal?

a friend and I play a pokemon-browsergame, which also offers monthly subscriptions for premium currency and benefits (=real money invested). We are also on a discord server with some friends, where we talk about the game. Note: this is a privatly run server and has no affilation with the game, the mods or anyone besides us.
One of the Admins posted something along the lines of:

“Don’t generalise. “Only the sith deal in absolutes” may be from sci-fi, but there’s a very real truth to it.
Bad cops suck.
Good cops who do things RIGHT, don’t.”

On our sever (again, not the site) my friend just jokingly wrote

“Bad Nazis suck.
Good Nazis wo do things RIGHT, dont’.”

Because they disagreed with the above mentioned statement. So apparently we had someone take a screenshot, send that to a moderate on that site and my friend got now permantly banned and no refund of their monthly subscription.
The reasons they gave were about toxic behaviour and rudeness. I also don’t agree with my friends statement, but it was a hyperbole and was in no way meant to hurt someone. Alas, they refuse to talk to them or let them explain. The permalock is final.

Sorry for the long explanation. The question here is just: is there anything they could legally do here? (for context: the website is based in the UK and in their rules they wrote the british laws apply). Thank you all very, very much in advance!