Because, treating our fellow gamers - of any origin, creed, sexual orientation or gender - with proper respect is not politics. It is basic human decency. It is making our hobby as welcoming to others as it was to us. Forbidding discussion of the fact that within our hobby they don't always get the respect they ought is harmful, and doing harm to gamers is not our thing.
That some folks call this politics is really not our problem.
The problem with ENWorld right now, and the problems that Morrus is encountering repeatedly, is perfectly summed up in this post I'm quoting.
This site is running articles repeatedly to fulfill their political need to "Change the world" and then thread banning or site banning people who don't share the political motivations behind the articles when they disagree or fail to meet the moderator's expected declarations of political alignment. Often with the moderators posting long dissertations about how misguided the people who didn't align with their politics are.
"Basic human decency" is ejecting people who attack others with slurs, or who demonstrate prejudices against other groups for the items you listed. That's literally not what you're doing. You literally just thread banned me for asserting that you cannot sell far left politics to conservatives. You literally quoted those 5 words as you announced you were thread banning me. Not one single word I posted denigrated anyone, and you're aware of that. I wasn't violating the "No Politics" rule anymore than every other poster on the thread, including yourself, and you're aware of that too.
Shutting down comments because people dared to suggest that law enforcement should handle accusations of sexual assault and not an internet forum based on RPGs, allowing people to demand social security numbers and photo IDs because they might be a sexual abuser for suggesting your articles are missing details (which we'd find out years later they were missing very relevant details) but banning people for suggesting something was off, allowing attacks on posters who demonstrate moderate or conservative values but banning anyone who uses "SJW" immediately, and myriad other examples.
So at least be honest about it. The moderation and permitted content on this site is based on the politics of the moderators, and anyone who makes the mistake of failing to uphold those politics is ejected. That's very different from a moderation policy of basic human decency.
I'll also point out, in closing, that your moderation policies are doing more to harm the hobby than anything else right now. All you're doing is entrenching people in their values, and costing RPG companies sales as they opt-out because the community is so exclusive towards those who don't share far left politics that they decide the hobby isn't worth pursuing. When they leave, they take multiple people with them, their whole gaming group will go.
So really, my advice is, pick one: Either this is an RPG site with a No Politics rule and start shutting down all political discussion, or update the rules to make it clear that this is a left wing RPG site that doesn't welcome conservative or moderate view points and continue on your present trajectory.
Your site, your rules, your choice. I'll respect your decision either way, as I firmly believe you have the right to decide either way.
But make it clear to me and others what this site is about. Because it's really unfair to claim it's a No Politics site while moderating very politically.