Is it normal if parents don't care that their son is a heroin addict

is it normal that when i tried to help my ex-boyfriend who has started doing a lot of heroin by intervening at his house(and he has been for almost a year now), after i caught him lying to me about being somewhere else and blowing me off, his parents completely ignored my yelps of pain when he tried to physically throw me out of his house so i wouldn't tell his family? i tried to talk to him first! when i realized there was no chance i could reason with him, i thought it would be best to tell his stupid parents who LIVE with him, but have NO idea, that their son is a heroin addict. i still care about him and so i thought it would be more selfish of me to not tell anyone because he graduated from college over a year and a half ago but hasn't done anything except move back in with his parents, play online poker, and support his new addiction.. but all that aside, i learned my lesson, i knew he was out of it because of how violent he became with me..

but my question is about how when i showed up to his house, he managed to rile up his parents and his friend (that does drugs with him) like sheep and he got them all to HIDE from me! they turned out the lights.. i kept ringing the doorbell because i saw them inside before i parked. why didn't they think he was acting more crazy then I was?? they've always liked me (we went out for almost 4 years), so when i show up in a bit of a panic, why would they not trust me but RATHER hide from me when HE'S the one acting so differently and i've never acted "crazy" like that before-as he convinced them i was.. i can understand a drug addict but is it normal that his parents ignored helping me when they could CLEARLY hear he was hurting me? what is wrong with them? I ONLY WANTED TO HELP HIM.