Well. I would suggest you to visit a psychotherapist (first just you- the parents). The psychotherapist will give you some really good advice how to deal with these situations in future. The next step would be to bring your son to the same or other psychotherapist. He has to accept hes sexuality and learn how to deal with it. Hopefully he will be encouraged to build relationships with people same age as he is. Ant this will be the long lasting solution to this problem- as soon as he has relationships and can live out hes sexuality, there will be no need for the things he is doing online.. Please dont be mad, be trusting and supportive, give him back hes phone. Of course all adverse reactions from you will cause adverse response from your son. That is the same as if when someone said candy are not healthy, so you may not carry them in your purse. We will take your purse away from you and later give it back on probatory period. But you love candy so much. It makes you feel good. You know it is not healthy for you. This stresses you. And now if your parents add to this stress by making comments or try to talk with you about it without having good, working solutions etc. you will lash out sooner or later. Help your child! He needs your support now the most! Or you will loose the connection. Good luck!
I'm late in reading this but he'd lose all ability to access internet at home and parental controls on anything outside of the home. sure, he could participate in this type of thing outside the home but this would slow him down. I'd also attempt to get him involved in a school activity so he has less free time to mind wander to such things. And that he is disrespectful, it goes with the age. But for his own safety, he's proven he can't be trusted with technology or social media. So, he'd lose it if I were his parent. Hang in there.