Because, A, "they" had a masculine (a term in this case I use very loosely, more of a whiny soy boy) voice, and because B, (s)he physically attacked me. Don't get me wrong, there are a few of them I'd love more than anything to see their heads on pikes, but I won't respond forcefully without provocation.
Basically, I don't enjoy the thought of killing Liberals. However, I do enjoy the thought of killing terrorists. Antifa, who engage in unlawful intimidation, assault, and destruction, for the sake of pushing their twisted political beliefs, qualify by definition as terrorists.