I don't understand the logic behind this useless argument. Everybody who has this argument makes it seem like you don't find baddies in General chat trying to form your group.
Baddies will come regardless of which method of random group assembly you use. Your only guarantee for a non-bad group is ti form up with a group of friends, and if that is what you're doing, you don't care about LFG or General chat either way.
Plus, it ignores that the vast majority of groups that form using WoW's LFD tool complete the dungeon successfully without issues.