Years of bad faith argument by professional high school bullies does that. Years of spreading hate and intolerance to their "others", but shock and horror whenever someone didn't tolerate them. Years of snide comments or glee whenever there was an attack on someone they didn't like.
I really didn't care when Paul Pelosi was attacked because people like him don't care or even notice when someone me gets attacked. Why should I care at that Kirk was attacked?
People are saying that this attack with spark more violence, but it didn't really matter that Franz Ferdinand was shot. WWI was going to happen some way or another. Whatever happens next was going to happen one way or another.