That's really a myth about Columbine, one of many that have gone on over the years. Eric and Dylan weren't bullied. They weren't outcasts. They weren't part of a "trenchcoat mafia." In fact, they were quite normal. In the typical clique hierarchy, they were pretty much in the middle of the pecking order.
Eric Harris and Dylan Klebold were bullies and thugs by any definition. Eric harassed Brooks Brown to a point that the Brown family was scared. Yes, scared s***.
I actually remember reading an article that the “Trenchcoat Mafia” did not like Harris and Klebold, particularly Klebold because he was anger prone and extremely belligerent. I have to fish for that though because it has been a while.