Lyte, I want your opinion on premade harassment

In my last game I was matched with a four man premade. Normally I don't care but it was One for All and when my pick won the lottery pick they said they were going to report me for my shitty pick and berated me and my pick. We get in game and they offered me no support in anything I did and when I died I got "pick Elise and is shit with her". I don't know if I was reported or not but it pisses me off that premades think they have some power to bully people and threaten with 3-4 reports. Are these threats reportable? Is there a system in place to know the difference between premades reporting a player just to be assholes and legitimate reports?