First, the person was only given a community ban, and not even a permanent ban.

Second, people absolutely should feel that spreading genocide denialism isn’t kosher on any legitimate instance. If it was an instance ban, I’d be in support of it, in the same way I would support someone playing debatelord games about the fucking Holocaust should get the boot. It doesn’t matter even if they do ‘genuinely’ believe in their genocide denialism, it is not and should not be welcome in any civilized space.