Here is what I think is something of a crux here:
Is more harm done by 1) someone innocent erroneously being removed from a game, or 2) someone malicious being allowed to remain?
That is, I think, part of the fundamental difference of opinion happening.
Yes, the US courts (and I assume others internationally, idk) say a person is innocent until proven guilty. Yes, that it is an incredibly valuable legal principle to use in actual criminal proceedings where the cost of declaring an innocent person to be guilty has severe consequences for that person's actual live.
But this isn't a court of law. It's an online hobby game. Big games in this instance might have a playerbase numbering in the hundreds; a lot of the games discussed here are more in the tens or dozens.
My view is that more harm is done by the malicious player allowed to remain. Hugely so if that player is someone who has actively stalked or abused another player. Being stalked is active, real-life harm. It is severe, in a way that being removed from a RP game simply isn't.
That does not mean that you have to simply believe each and every report that comes your way. There is a measure of common sense to be deployed here. If you have a long-term player who has a visible history of getting on well on the game, who does not have a history of making a lot of complaints, such that receiving a complaint from them is notable -- that is very different from receiving a complaint from someone who makes them regularly and frivolously and who maybe has had more than one complaint made about them. Someone making a clear, serious request involving stalking or targeted harassment is different from someone making a request about not getting along with someone. Yes, absolutely engage in judgment and critical reasoning here. Absolutely. But if a player's history on a game points to them being generally above board? That's also a form of evidence.
There are very, very few methods of providing evidence on a game in a manner that are 100% reliable. I know that Ares has built-in tools. Not every game is built on Ares, and any bad actor can easily avoid putting their efforts into places that can been directly reported on the games that are on Ares. If these are the only methods of evidence that are acceptable, you will be leaving countless openings for bad actors to exploit. If the answer is that any other avenues will likely be off-game and not policeable, I think that's a bad answer that favors manipulators and harassers. Yes, you may have to take a critical eye to evidence that's presented, and that's fine. But rejecting it out of hand as being outside the scope of a game's staff isn't.
As for staff favoritism: if staff are going to behave in an unethical manner to favor the people they like best, neither philosophy will make a difference. It will be an issue on both sides of this philosophy divide. No amount of evidence requirements will get around this if a staffer wants to give shinies to their friends.
As has been stated, if someone is being stalked or abused, and they are given hoops to jump through in order to avoid their abuser on a game, they will just leave. And maybe that won't impact the game in the grand scheme of things, and maybe it doesn't impact a staffer personally. But it is a form of violence on the victim's life. It is one more place of fun, engagement, socialization, and community that is now lost to that person due to the systemic efforts of their abuser.
And I don't want to be party to that. It is, in my view, a far greater harm and moral failing to allow that to happen than to potentially ban an innocent player.