Ok, let's make it hypothetical (and I think it's worth discussing because there are other examples / it will happen soon anyway) - is the blocking by payment processors on more-or-less arbitrary grounds good idea? Don't THEY have the monopoly? (not treating BTC & co. seriously, sorry)

Because I (as I think most people) would be fine with the Patreon ban, had the payment processors' cartel stayed neutral (in our theoretical case). But once they side with Patreon, it is truly complete deplatforming, that you can't really solve by going to "another, more permissive, website".

And that is the real problem.