Over the past half decade, we have seen elected republicans invite Ted Nugent to the white house after he called Obama a "subhuman Mongrel" and made suggestions about him and Clinton "sucking on his machine gun", post videos of various republicans physically attacking both symbolic media representations and opposing members of congress, and has called for Pelosi to be "executed".
Yet those republicans continue to be supported by the party at large.
I think any sense of decorum or integrity has been gone from politics for a long time. If republicans are going to engage in violent rhetoric, it shouldn't be surprising if others decide that its fair game.