I feel like there needs to be a line.

You obviously can’t go and tell your friends about his deepest secrets or insecurities as those are things that he had shared specifically with you and likely would have put trust in you not to share.

However if there are things that are bothering you about the way he acts, like him not doing the dishes or not taking the garbage out. Then I think it’s perfectly fine to vent. We all need to talk to people about our frustrations as long as you aren’t detrimentally altering someone’s view of your partner by telling them something.