There's nothing here to forgive. If you don't like shows with sexual content and violence, you don't have to watch them. But you can't expect him to change his interests because they don't match yours. Game of Thrones is a good show, I love it, but if someone didn't like me because of a show I watch, I would regard them as incredibly shallow and naive. Telling his parents would be the worst thing you could do, he won't forgive you; rather, he'll see you as a hindrance in his life and someone he can't trust. Think about how you would feel in this situation. Let's say you are watching a show that he thinks is inappropriate, tells you that he can't forgive you for this and tells your parents behind your back. How would you feel? Would you want to continue hanging out with this person? Would you trust them?
The other thing to keep in mind is type of curse words he's using. To be honest, words like sh*t and f*ck are really not that bad, they're just words that we've attributed negative meaning to (I'm always reminded of that South Park episode where they highlight the right and wrong way to say the word sh*t).
If he's using language that has been used in a derogatory fashion to harm someone or marginalise a group of people (i.e. F*g, or N*gger) then that's an issue that should be addressed. But whether you are the right person to do so is the main question.
You might really like this guy, but you mentioned you just started highschool. So you're young and have the whole world to figure things out. Like others have said, let it go, move forward and get involved in clubs/societies with like-minded people so you can have positive and not negative experiences.