I'm going to steal my dad's medical marijuana and smoke it with my boyfriend
Why would you steal your dad's weed?
I'm upset with him because he wouldn't let me go out today.
It is understandable to be upset that  you didn't get to go out but you shouldn't take it out on your dad. He might have a good reason for not letting you go out. Taking his weed might be too much.
Don't be a jerk and try it. It's only weed, who cares? I'm bored, I want to do things.
But since it is medical weed, then your dad might need it form medical reasons. You should consider that it could have affected his health to steal his weed.