That isn’t just on the left.
If you said on this site that you didn’t agree with the patriot act, or the Iraq war, you were banned. Now it’s the complete opposite. Just two examples.
Before my time. I lurked periodically before then.
Also, Bill Buckley et al. managed to cancel and ban Sam Francis, Joe Sobran, Peter Brimelow, and Buchanan, for positions that everyone except the GOPe now accepts.