The justices of the supreme court ruled that Trump was immune and effectively above the law while being president. What is now stopping Biden from bringing a gun to the next debate?

If inciting an insurrection towards their own government is an action without legal repercussions, I don't see how the law would be less lenient about straight up firing a gun at an opponent.

I by no means want any party to resolve to violent tactics. So even though I play with the thought, I really don't want anything like it to happen. I am just curious if it's actually the case that a sitting president has now effectively a licence to kill.

What am I missing?