Do a search here for any article involving CCW laws under consideration. In nearly every article, there is some liberal predicting a scenario like the ones I listed. I simply picked their favorite three to cite.
Wow, I can't believe you're really challenging him on that!
This is what I'll politely call "common knowledge", along the lines of "the sky is blue".
If some nabob comes riding in demanding incontrovertible scientific proof "that the sky really IS blue", I'd tell him to get stuffed, and he'd have to be the biggest fool in town to not realize it in advance and keep his piehole shut.