Since you brought up something about Crowder being hated by a huge percentage of the population, which was a quip that had no relevance - I decided to give you a quip that had no relevance.
But the basic reason that he should be cancelled is the following:
If Congresswoman Omar was assassinated and it turns out to be a far-right maniac, then the right, far right and moderates will all tell you - he was a far right maniac and it has to stop.
The left is basically saying I hate Charlie Kirk he deserved to die, and by the way it was your own guy.
I get that Kimmel did not say the first thing, but he repeated an extremely dis-proven concept that the shooter was right wing.
He was dating a trans person, the bullets had markings bella ciao (that was also sung in disrespect at CK vigils by the way) and his dad and other family members have confirmed he was radicalized left.
If top-level people on the left refuse to acknowledge this, it's pure lies and fake news and needs to be cancelled.