Weird just means unusual (with slight negative connotations already) . So to use "weird" as an unqualified insult is to say that being unusual is a negative thing in itself. Which echoes the sentiment behind things like xenophobia and such. That's why people are uncomfortable with this line of political attack, imo.

To say "there's good weird and bad weird" doesn't say much more than that there are ways of being unusual that you view positively and those that you view negatively. But that's obvious and doesn't resolve the issue I mentioned before.