I understand where you're coming from and that it doesn't feel good to be up against this kind of thing.
On the other hand, I think that if you want to get better at the game, it's good practice to do things like maximizing your points on the last turn of the game. Dominion was a tabletop game before it was anything else, and there's no point counter telling you exactly what the score is. Also, that point counter reflects the current score, but various things like exchanging travellers or returning Encampments to the pile can affect the score of the game once you press that "end turn" button.
So like, if I forgot about that, or whatever other reason, I would want to maximize my points when I'm ending the game. I can't tell you how many games I've lost to a miscalculation like this, even with point counter on. I lost a game because I thought I was emptying the third pile when it was really the second, and even though this was hilarious, it taught me a valuable lesson and I've adjusted my play in ways like this to compensate. Building habits where you do this every game is the best way because the whole premise is that you forgot those things were there, so if you act like they're always there, you will forget less often.
So I don't think removing these people from the community is the right choice. If you really have a problem with this, there's a personal blacklist feature that you can use so you are less likely to get matched up with these people, and I'd encourage you to use it.