As an additional point; “weird” isn’t a slur. A slur is an expression where the very words themselves are considered obscene - a slur is offensive, even when it is used to describe someone or something according to its strict definition.
There is no context where describing someone as a “removed” or a “retard” isn’t offensive. “Weird” isn’t like that, as you’ve pointed out - it’s being used as a simple insult, and it’s persistent because it seems to really annoy the people it is directed at
Edit: to further my point, one of my examples is so objectionable that it was automatically filtered from my post
Way back when I used to go to the football with dad - kids under 5 could take the train for free, but weren’t allowed in the stadium, so I was 4 on the train, and 5 when we got to the stadium