I believe the point they are making is that “sure guns are the easiest path until you ban guns, then something else (seemingly cars is suggested) would become the easiest path and therefore would be ‘switched to’ by those wishing to cause violence, as their violent ideation was not dealt with merely the tool was, so now the tool has changed.”
I.e, most people hammer in nails with a hammer becuse it’s the easiest path, but if you ban hammers and I need this nail in this wood, I guess I’ll use the back of my wrench. Sure, it isn’t as good but it’ll work just fine. I wouldn’t say “oh well nothing can be built, guess I won’t build shit,” if I’m significantly determined to get that nail in I’ll do everything in my power to do so including using tools not exactly meant for the job but that’ll work.
One could make the argument that “at least it takes me longer to build the thing,” or “you’ll be able to build less things,” but that is only true assuming I downgrade to a wrench. I could make my own hammer easily, or I could upgrade to a nail gun (in this analogy I guess that’d be a pressure cooker and some nails Boston Marathon style.)
They do not seem to be saying “cars are more effective than guns,” imo, though it seems to be taken that way by (possibly you and) others in this thread.