no, if someone's notorious for their shitty exchange behavior in other exchanges OR notorious for being a nazi creep, it's fine to ban them.
there are lines to this. i once had a very awkward convo with a friend because they wanted me to ban this entire clique of people from discord because they'd behaved poorly in a wank with one of the friend's friends. i drew a line there and said that i expected them to behave in my server but wasn't going to preemptively mod. these are the decisions you have to make when modding anything. but, in an exchange, where you are definitionally going to be interacting with others, it's fine to ban people who are known, specifically, for poor exchange behavior.
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there are lines to this. i once had a very awkward convo with a friend because they wanted me to ban this entire clique of people from discord because they'd behaved poorly in a wank with one of the friend's friends. i drew a line there and said that i expected them to behave in my server but wasn't going to preemptively mod. these are the decisions you have to make when modding anything. but, in an exchange, where you are definitionally going to be interacting with others, it's fine to ban people who are known, specifically, for poor exchange behavior.