Dear lord..sound EXACTLY like this kid that showed up on 420 last year..

He walks up my stairs and walks past my mom, as he's doing that he takes off his shirt and drops it on the floor in the middle of the hall, then as he's walking in my room still near my mom he says extremely loudly "SMELLS LIKE MARIJUANA IN HERE" (like your friend's parents, my mom doesnt care she just doesnt want to hear it being screamed throughout the house)...i let him stay for a smoke and kicked him out promptly. Your guy was a total dickhead too. Kick him out and make it clear that you're kicking him out, not saying 'see ya later'.