I think this is actually the big problem in the debate, not "cancel culture" or "heresies". A lot of people seem gleefully enthusiastic about seeing the worst in other people. This is not isolated to just one ideological side: people on the right engage in it just as much as people on the left.
I've started to seriously dislike "dog-whistling". Often it's "yes, what they're saying is looks fine on the surface, but I know their actual secret motivations!" Yes, things like "14/88" and whatnot really are "dog-whistling" and it's fine to call it out as such, but 9 times out of 10 I see it used today it's weird assertion about someone's motivations. It's essentially a straw-man argument with extra steps (allude to a far more extreme position than what was stated, and then attack that).
Sometimes this goes so far I wonder if I somehow don't understand the English language correctly, or ... something. Many times I see people commit a "heresy" it's something fairly mild – or even completely benign – taken to far more extreme levels than what it seems to mean on the surface.
In this specific article it seems clear to me that Graham isn't defending tosspot Nazis or other overt "x-ists", yet here in the comments we have people who seemingly take this to mean that Graham is defending folks who say that "people with different skin colors are dumber" and similar things. You can read that in his essay, I suppose, but only if you come at it with a certain attitude.
Once you eliminate the "this person is x-ist, let's find arguments to support it"-attitude the whole "heresy" problem goes away, too. I haven't the foggiest how to actually do that though.