My dad found out i've been smoking weed and he went crazy. Let me  tell you about my background. I am a second generation christian. grew up in a christian family, went to a christian school untill college. Im 22 this year, and still living under my family. My parents are both hardcore christian, but i am not. Im no where from being a christian apart from the fact that i lied to them i go to church every sunday. I've been smoking weed for a year. Finally , today my dad caught me, came back from work early. They have been suspecting me for this few month already, but i didn't take that hint too seriously.

Now, my dad is saying weed = cigarette, and is telling me stories about how my grand father died because he was a heavy smoker. I told him, he is wrong, and weed is not cigarette. He even said that i will be addicted eventually. To be honest, the only reason why i smoked today is because i finished all my assignments and next monday is my 2 week study break. So i have this 3 day period to chill and play dota. I am honestly not addicted to weed, and you can't be addicted to it anyways. My dad just didn't listen and it is hard to tell him anything. He even asked me if weed is like a guilty pleasure to me, i said yes. and he was stunted badly. He was lost for words and i think this is the max he could take. He walked off the room and told me that he is not going to talk to me anymore until i change my attitude. 

I can understand from my dad perspective, as his dad was a cigarette smoker, and his sister died in a car crash because she was drunk. So he had all these bad memories about smoking, alcohol and drug. But i told him, i don't do alcohol or smoke cigarette. weed is different from those. He still didn't want to listen to me. T he only reason why i didn't tell him was because i was afraid he will flip out, which he did. He asks me if i will continue doing it. I answered him, i wont do it in your house if you insist. 

im not sure what should i do now. How do i even calm him down..