Here's an interesting dilemma. First, I think that US centered professional groups/conferences need to expand their Code of Conduct to include support for democracy. e.g. Don't affiliate with people or organizations that fund (or whose owners) fund anti-democratic politicians.

Second, I'm a member of a prominent group that a year or two ago couldn't agree on even a basic Code of Conduct because some members had (to be polite) 'alternative' perspectives. What to do?

I have made it clear in other groups that if those anti-CoC views are followed, I can’t be part of them

Yep. It's pretty difficult to justify being part of a group that refuses to have a CoC. One key take away of Jan 6th is that tolerating the intolerant is bad idea.