If the Klan were riding into my town, I'd feel better sitting on my porch with just such a weapon as you mention. My wife's ancestors found themselves in just such a situation, and successfully defended themselves, though I don't know the details of the weapons either side had. In eastern North Carolina where some of my ancestors come from, the Lumbee Indians ran off the Klan with firearms. Unfortunately, we are entering a time where these types of interactions are more likely to occur. The bad people have already armed up, and I would not want to discourage the good people from doing so, nor encourage a good liberal to disarm. To me, it is not about gun collections, or hunting, or target shooting for fun. But everyone has their own individual reasons.

That being said, you do have a point. Governments are established in part to protect the public safety. They do this not only by prosecuting those who have committed crimes, but also through some degree of regulation. Surely we would agree that nuclear weapons, or nerve gas, or fully automatic weapons, should not be in private hands (but neither in police hands). The right to self defense must be balanced against the protection of public safety. So are all of our rights. A person whose home is not subject to random search due to the 4th Amendment could be stockpiling ammonium nitrate, which could be much more lethal than any firearm. But there are regulations on the sale of large amounts of such things, sales are tracked, etc., as they should be. Hopefully you and I could have a discussion on what constitutes reasonable regulation of firearms. When someone (like the OP) says that anyone not in agreement wants for massacres to happen, this is not conducive to a reasonable discussion.