The M2HB (aka Ma Deuce) is a Browning designed, .50BMG, air-cooled MG that's used all over the place, including in Iraq by US troops. AFAIK, if it was made before 86, it ought to be transferable to Joe American. Manufactured after that, it would have to be transferable from SOT to SOT. There are probably semiauto clones out there too that a tv show with an agenda wouldn't hesitate to label as a MG.
I don't doubt that they edit it so as to choose bits and pieces that suit their agenda (whether that agenda is anti-gun, promoting ignorance, or spouting what they think will keep up ratings -- often it's all three). That sort of nonsense goes pretty far with the average viewer to further the myth of the existence of a so-called "gun show loophole." It also wouldn't surprise me a bit, judging from the ignorance I've heard spewed at gun shop counters and fun shows, if that's how the interviewee thinks things work. Or maybe he just got an ATF Gun Runner special. The process of buying NFA items is pretty clear cut. I don't think it's tremendously difficult but it certainly isn't cash and carry.
Have fun at the gun show and let us know if you find anything good. Those places are full of ears that don't have a shred of a sense of humor between them though, so don't even joke with the dealers about converting semi autos to full auto, not passing a background check, being a bad guy, being from out of state, etc. to see their reaction.