We're all angry about this buy boycotting itch won't help anything, they're probably lost half their revenue from this situation, and might not even survive. We should probably be supporting them.
It's never quite that simple in cases like this, though.
If external circumstances stop a company form providing what you're after, how can you support them if there's no actual reason to use them. A similar, but not NSFW, situation would be a store being let down by a supplier. It's not the store's fault they aren't stocking what you want to buy but it doesn't change the fact that they aren't stocking what you want to buy.
It may not be a deliberate boycott but the end result is the same. There are people who will not use Itch whilst the current stance stands. For no other reason than devs won't go where they can't supply their games and players won't go where they can't buy them.