I think the problem comes when certain topical groups interpret their mission narrowly. Based on your other nearby comment, you mention your experience with a rock climbing group that doesn't so narrowly focus on rock climbing. I think that's the right way to do it.

There was one group I used to attend where I was definitely not as interested in the topic as others. I recall someone at the meetup said to me something along the lines of "If you don't agree with X then why are you here?" Well, I attended because I found a lot of interesting people there, and I know I wasn't the only one. Some organizers made the meetups unstructured conversation, which was great for me. Honestly, I'd just like to meet other people interested in a particular topic. Other organizers preferred meetups with more specific assigned discussion topics. I rarely cared much about the assigned topics and they made the unstructured conversation I wanted to have much more difficult or even impossible (particularly for the online meetups). I don't attend those meetups any longer in part because of the assigned topics.