Nah not really...
Tony didn't have to kill Manny though. Manny stood by Tony's side even when he gave him his ass to kiss.
Gina really loved Manny over time just like Brian loved Mia on F&F. Having Manny take Gina home while he was in the club was smart too. Gina or Manny could have been caught in the crossfire of the attempted hit by Frank.
If Manny had gotten Tony's blessing rather than sneaking around his back during the second half that movie, things would have been different though.
That Coke was affecting Tony's judgement too. Unless Manny was leaking info to the police as a way of getting back at Tony, I don't see why he should have killed him.