Retweeting is not an endorsement of the tweet itself, let alone of every single comment made by that person.

Retweeting without comment can be assumed endorsement, generally. And retweeting a group that on plenty of issues goes against your stated beliefs is, at the very least, a bad look. If I'm going to share something from someone who is ideologically opposed to me, I'd certainly want to couch it in something like 'I don't agree with them on much, but they're spot on here,' or something to that effect.