AITA for removing someone from a Heroic dungeon group for harassing players with low dps?

I was tanking a group through Gundrak H and pugged a rando level 80 that spent the first few packs complaining about one of the members low DPS, (saying they are bad, they should go back to retail, youtube their class), and by the time we downed the first boss(which we did without issue) I lost my shit and removed him from group, which sparked a litany of whisper harassment from the player in question and subsequent trash talking about me in trade chat for cheating him out of a lockout.I ensured the group finder was flagged for friendly to new players before listing, as two of the players I was guiding through the dungeon were fresh 80s and had never tackled heroic content before.Am I the asshole for removing this individual and costing him a lockout?