I don't even think there is evidence to support either side of that argument. Party lines aren't cut and dried. Plus, it doesn't even matter. There is no reason to draw lines in the sand. Criminals are criminals. It makes no difference who they voted for. At least, it shouldn't matter.
How can he make such a statement. It's as if we are being torn apart instead of standing together against a common foe namely ISIS. We stand around pointing the blame at each other instead of standing together to come up with a plan. By saying such stuff we are only fueling the anger that is there between the parties and separating the party lines all the more.
Ted Cruz's statistic on violent criminals mostly being Democrats was not only insane and incorrect, it also reflected poorly on his general intelligence. There is no evidence for this claim, and the political affiliation of violent criminals does not present any kind of causal connection to their behavior. To imply that being a Democrat makes one more likely to be violent is crazy.
That is a ridiculous statement and no Ted Cruz is not right. Ted Cruz says many ignorant and stupid things - this is one of them. I suppose he was defending the NRA and going against gun control, but making stupid comments doesn't help one win an argument, just the opposite.