I'm rarely interested in passing laws against somebody's notion of how to do things that don't really hurt anything.
My problem with the use of a .50 BMG is that's not particularly a hunting gun. A shooting gun, yeah, but I pretty much figure that shooting what I hunted for is sorta up close and personal. Now, some might think my self-imposed limit for range at around 400 yards is longer than they'd shoot, but to me it's reasonably up close and personal.
Shooting something which is basically farther away than is readily or easily seen with the nekkid eyebone just doesn't sit right with me.
And hunting is supposed to be fun. Toting somewhere around 30 pounds of go-bang doesn't really strike me as fun.
So I wouldn't want to pass a law against it. But the idea strikes me as really silly.