Am i right to do this? or should i listen to my parents?

Screw them! LOCK THE DOORS (no offense) People are very irrational when they are drunk, that's probably why they get mad. But they'd probably kill themselves if you left the door open and someone came in and like cut you into little pieces why they were out getting wasted. If they want to get back into their house at 2 or 3 (or whatever frickn time they want) then they need to take a key with them!!!