If a police sniper shoots a mass shooter in the middle of their mass shooting, that's a hero. Not a villain.
We have to do the best we can to be kind and minimise suffering, while understanding that there will inevitably be a diversity of judgements on moral matters. And if those moral judgements have real-world effects, there will be moral judgements about that too.
The lack of moral universality is how it is, not a failure. And it never ends: there are no right answers, although there might very well be wrong ones. Its up to us.
I don't mean this as a "gotcha", but as a reminder that morality is a human invention, and different humans will take different moral stances on things.
But even if it is, in fact, a thing - it's clearly not backed by "one particular moral judgement", as it is commonly portrayed. Lots of people face disapproval and punishment for a diversity of chosen moral stance, including people who could be categorised as "liberal" and who are typically considered to be those doing the "cancelling".
Supporers of the abolition of slavery or apartheid, or of human rights for minority communities, were for many years "cancelled" in the US, and in Europe, for example. Today, in the US, supporters of social equality and diversity are being "cancelled".
So I suspect that "cancel culture" is what you get when one moral/political group (of any persuasion) only sees part of the bigger picture, and uses that to manufacture a grievance.
Now, the worst and slimiest amoung us are crawling up on the cross and weeping and gnashing their teeth because people won't buy their book or watch their movie. It's almost always the most powerful who claim to be 'cancelled'.
Calling out assholes is a good and useful function and we should continue to do it.