Is he right to be mad?

Let me try to explain better lol

Is my bf right to be mad that I smoked w my male cousin? In his head he sees it as I don’t fuck with him like that, like all crazy about him.

Because when I was dating my baby daddy. I used to smoke weed with him.

I think he’s being ridiculous. I’m not really a smoker and it took me 4 years being with my ex to smoke with him.