I mean, yes, that guy is never going to be convinced. I guarantee you that no one involved in the production or distribution of that video held any hope at all that they would get anything but silence out of him even in the best scenario.
But it's not about that guy, its about the people who see the video. Like you do this IRL at thanksgiving or whatever and it is basically worthless, but then you are not trying to persuade a national audience with from a wide political spectrum that your jack ass uncle is a bigot hypocrite. No one's watching and deciding how they are going to vote in 18 months on if uncle jackass (or his political party) gets to genocide trans people.
But John Stewart has a national audience from a wide political spectrum. If he can convince a few hundred people now that the right is full of hypocrisy it might make the difference 18 months from now. Non disruptive, non violent political action is theater. You do this to play to the audience, not because you are delusional enough to think that the other side means well.
And we can't shut them out, they have a god damn 24 hour news network dedicated to spewing their propaganda every second of every day. If we are not doing something to counter message that propaganda we might as well give up, and part of that is making them look like the bigoted hypocritical jackasses they are. This is one of many tools in the toolbox for how you counter message propaganda.
And a second thing. The "just kill these people" comment. I'm not going to condemn it, to be clear, but there are few things a person can say in the political sphere that reads worse to me. I don't think it is intentional, but what this actually says and how people react to it is as if it were "we can't win, so just give up."
You see, "just kill these people" is actually an option, at least in the USA. Ironically, republicans have gone to great lengths to make absolutely sure that you can get a weapon to commit a murder. Any one of us could get the weapons we need to, well, do exactly that. But we don't for so many obvious reasons, and I know this because I'm not reading a list of political figures murdered every morning.
In absence of actual violent action, anything taking the form of "Don't do non violent thing X, it does not work, instead do violent thing Y" is a call to give up. Because no one actually expects anyone to engage in violent thing Y. They only expect them to give up non violent thing X. What is actually being said, intentional or not, is "give up on X, and replace it with nothing."
I'm not going to say violence has no place here, because I don't believe it. But knowing what place violence does have is important, and constantly invoking violence jokingly alongside non joking discussion of other political methods dilutes the concept.