The left doesn't believe that. That's just the message they want to plant in the minds of their useful idiot liberal dupes. The left is all in favor of war and violence when it comes to revolution.
You are correct, but the thing is that no matter how much they lust for violence, virtually none of them have the necessary training, or the weapons. If it came down to street fighting, we'd have the advantage. Of course, that assumes the military either sits it out or joins our side, which would technically violate the Constitution, but would be necessary to have any hope of the Constitution.
The problem is, I don't think they'll try something like this until they've taken the guns...so if they try to take the guns they need to have a furball on their hands immediately or we're all in deep trouble.