I bet it's the "mild centrist" position of the world taken as a whole. (I mean, it's not like wishing people dead is uncommon - people do it about people who cut them off in traffic.) It's the US that has shifted the Overton window to the right, not this forum to the left.
Seriously, the loss to Trump of being assassinated is miniscule compared to the harm to the world of him not. Utilitarianism is not an obscure, radical moral theory. The best case assassination opponents can make is that him getting assassinated would've made his followers go crazy, but more popular figures than him have been assassinated without that happening.