What is excommunication but formalized cancel culture?

Both sides can and do engage in it. It's worth condemning regardless of where it happens. And yes, of course, it's easier to see the mote in thy neighbor's eye than the log in thy own.

"What about Ted Cruz" isn't an argument against leftist cancel culture, but it is an argument that the right wing needs to restrain their own illiberal extremism the same way the left needs to restrain theirs.