Bayonet lug is NOT an evil feature.Blaster is right to a point. You can have a folding stock all day as long as you dont have a flash hider, bayo lug or granade launcher on it as well.
( edit I may be wrong on the bayo lug )
And so long as the folding stock is not designed to permit the firearm to operate as normal when the stock is folded, it doesn't count as an evil feature.
Thus, folders like the LAW Tactical that blaster mentioned do not even scatch the surface of being counted as an evil feature.