'No prizes for guessing which colour tie those people tend to wear.'
I doubt if anybody has any idea what the real numbers are, but I've met supporters of just about all political parties that abuse workers. It isn't (in my experience) limited to a particular set. Also, bear in mind that extreme left and extreme right are as bad as each other and actually abuse the population equally. Stalin wasn't any better than Hitler. Pol Pot wasn't any better than Franco.
The idea that left(ish) people are nice and right(ish) people are horrible is massively misleading. There's bad on both sides of the political divide.