While I agree entirely that they're not free per-se, if it weren't for them, there would be nearly nothing to post for anyone who doesn't want to use the Epic Games Store.
Lemmy communities are already at a disadvantage to subreddits in terms of attracting and retaining users, so I don't think fracturing communities further than they already are across instances is beneficial.
While I admittedly haven't tried using Arctic's regex filtering options yet, if other Lemmy clients have similar functionality, I would imagine a filter for any post that includes "[Prime/" or "[Prime]" in the title would automatically hide the posts without the need for community fragmentation.
If that was indeed the reason, then that only serves to support the notion that general disagreement, rather than just extremism, is what is being banned from that community. They have every right to ban advocates of genocide for extremism, but in no way do I think that supporting Palestine without supporting Hamas is a position worthy of a ban.