"Not particularly saying anything terrible, he was calling his team bad and telling them what to do."
When I read it reminds me of the:
"anivia go bot" [looks like minions will take it, but it's either at low health and not worth saving or just plain fine for a while]
"ugh, why did you clear mid" [ally was en route, but wouldn't make it in time to prevent a large amount to tower damage]
"why did you teleport top?? so bad" [turned a close 2v2 into two kills no deaths]
"i told you to go b, you noob" [saving our other carry so they didn't get his killing spree gold, killing one of them in the process, and crippling the team's mana]
"and telling them what to do." did not in any way imply constructive criticism, and is something that detracts from my gameplay whether or not cursing, raging, or racial slurs are involved.