You’re really looking for a straw man argument for this, and I don’t even understand why. The release and reception of this song is vile, there is no need to try and grandstand and go “actually…”

You’re allowed to say something is fucked up without having to mention everything else fucked up and discuss which is more fucked up. You’re wasting energy on the stupidest thing.

we see a comedian triumphantly holding up a bloodied, decapitated POTUS head with a look of cold indifference on her face and we say

You’re dead / You’re canceled!

(That’s my only contribution, noting she received death threats & hatred, carry on otherwise I just remembered that one)

It encourages violence, it desensitizes us,

We can understand why that's like, not a very concrete justification to be against espousing violence, right? I also find it weird, right, that we're doing this step-around thing, where you're calling everyone out for the hypocrisy of, oh, well, people are against this violence, but they're not against this violence? Have you maybe considered that the two forms of violence are distinct? Perhaps that the two forms of violence are actually not similar? That people have reasons for, say, wanting violence against one party, but not another?

That's what they're commenting about. You say "it's either all okay or none of it's okay" because it encourages violence, right, but, I am giving you an opportunity to show your work, when it comes to this very basic claim, upon which rests the rest of your argument.