The cheap response is to whine about "no true scotsman" but I'd love to see ideas on how to prevent groups actually getting corrupted in this way; it's probably in the "how do we create world peace" level of problems but the cycle is getting very wearing!
The major problem with the left leaning political spectrum in america is a somewhat blind authoritarian “respect” for “diversity” where what counts as diverse is rather restricted and generally doesn’t include disagreement on the subject.
The key missing ability is getting people to empathize with each other and not to confuse radical ideas which one finds abhorant and moderate ideas one finds disagreeable.
A cheap way to make this much easier is to ban labels like political party, gender, etc. If you stop sorting people (and yourself) into bins it becomes a whole lot more difficult to be so polarized as you aren’t dividing the world into us and them by dealing with a new human one by one.
I hold a very special loathing of anyone that weaponizes process in order to control others.
"The best lack all conviction, while the worst, Are full of passionate intensity".