It's terrible that you had to put up with that, but you really should just report and move on. Taking away the ability to use non-5 premades would severely reduce Riot's new-player influx, since a lot of people rely on their friends to learn the game. League is incredibly difficult to learn on your own, and it's ridiculously frustrating to lose without knowing what you did wrong. Preventing people from playing with their friends is only going to scare away newcomers, and the game will die.
I know, for a fact, that I personally would not play if I couldn't queue with my friends. There are good odds that none of them would either, or any of the dozens of people at my school who play. (About half the people who game at all.) This might benefit players by reducing trolling-- and that's a big might-- but the game wouldn't last very long.