Zac Efron -- Don't Question My Sobriety ... Or I'll Kick You to the Curb

Zac Efron doesn't have any problems with drugs ... at least that's what Zac Efron thinks, according to his friends -- who say anyone telling him otherwise is quickly 86'ed.

TMZ has learned the actor's friends are scared to broach the subject of Zac's sobriety ... because not only will they be ignored -- but they say anyone who makes an attempt is cut from Efron's life.

We're told Zac refuses to believe he's on a destructive path ... and one of his friends tells us they think he could become the next Cory Monteith if he doesn't get help.

As we previously reported ... Zac's friends say he never went to a real rehab facility last year. Instead, they say he received private therapy at a friends house.