Lets be honest here, we all have or have had team mates who we think aren't up to the standard, and have told our friends or other people that opinion, its not a crime to do so. For me, all 11 being best friends isn't important, and it does not, in my experience, usually doesn't happen. You don't have to like them all, nor even respect them, as long as you treat them in a proffessional manner and get on with the game. This has probably not been a secret within the dressing room for months, so why make a big deal of it now?
All KP wants to do is win, and if he believes some of his team mates are hindering those ambitions, why shouldn't he discuss this amongst friends (despite the "friends" being a little innappropriate)