You don't have to be accurate nor good to spray and pray and get kills with a SMG. People complain more about campers than SMGers, at least camping is somewhat more strategic then running around with your lasered SMG holding R. That is all.
You do realize that you've just said that the 90% of people playing this game who use smgs, suck, right?
People are right to complain about camping, particularly corner camping.
If it's true that we learn from our mistakes, then I should be a frickin' genius by now.