True Liberals, who are nearly all Republicans in the present era, believe in liberty. A belief in liberty makes political violence illogical. There is no reason to attack someone for believing differently than you, when allowing alternative beliefs is the basis of your whole worldview.
Socialists are different. They have ONE worldview, and want to coerce everyone else into it. This makes political violence extremely logical and easy. You can easily recognize who your enemies are, and, having a simple goal of 100% compliance, all tools are on the table to get them on board. This was the basic point that Saul Alinsky made.