You must know some very particular people, because I have met a lot of people who want gun control, but this is the first time I've ever heard someone suggest we might ban pitbulls.
That being said, I do think that people who are pro gun control tend to be anti breed bans, because in my experience the pro gun control folks tend to extend blank slateism all the way to dogs (it was the owner's fault for not training the dog properly, etc).