It may not be outright support but when throw in the mocking, sarcasm and continued expressions of hate it's damn near the same thing.

It's not the same thing. Any more than when you mock and ridicule and use sarcasm and make continued expressions of hate towards the left, it's not expressing support for the dude who killed the Hosrtmans. As expressed above, people can both believe that Charlie Kirk was a terrible person and that Tyler Robinson is a terrible person for murdering him.

I suspect that the fairly big reasons that "no one [is] expressing support for Tyler Robinson" is because a) would look bad given the world's reaction to the murder and b) would require some of them to pull off their masks completely.

This is, I think, why your discussions on this board are so unproductive. If you're not actually listening to what people are saying, and instead just treating them as if they were the imaginary different people you want to be arguing with, then you're going to be both frustrated and frustrating. You've decided in your head what everyone here "really" believes, and you're arguing against that - instead of paying any attention to what the folks here actually believe.