Didn't like the seme's friend made the uke feel like shit

Didn't necessarily make him feel like shit. He just warned him (with the truth). It was for his friend's sake and anyone else involved since the seme gets dangerous when his emotions run high. The uke was included in that warning for safety reasons.

It was never said, but I get the feeling the friend been around long enough to see him take care of others behind the scenes for the uke as it was briefly implied.

Sorry you'll have to remind me what manga this is for