The Psychological Community would tell you that watching forms of violence may just as well be a Cathartic Vent, as a Desensitization and cause of further violence.
I actually know a hell of a lot about that, since my Dissertation was ranked as a First (alone) and was all about Symbology of Violence.
If anyone wants to actually know what the Psychological Society would say...they may listen to my 15 month research into that exact aspect in a segment dedicated to it from my dissertation below.
Its known as "The Hostility Catharsis"
Someone oughta pass it on to the Senator in question, since clearly he hasnt done his research properly!