NOT being a fan of MG's to start with,I wouldn't put one of those things in any of my rifles if you paid me. I spent too much time humping huge loads of ammo up and down mountains to be doing much spraying and praying.
With the exception of ambushes at VERY close range (the only kind of amush there is),I have less than zero use for a full-auto firearm.
Having said that,they and the people who buy them are pretty much harmless. The typical street thug would just end up shooting holes in the sky,and the other people would rarely even shoot them. Have you seen ammo prices recently? You would have to be wealthy to shoot one,even IF you could find the ammo.
The BATF understand this at every level below headquarters in DC,where they understand nothing at all but pleasing Senators.
It is nothing but a scare tactic the BATF uses to fire up the Gomers.