At what point do I stop being polite and tell my (ex)friend to stop sexually harassing me?

I had a friend over to my house yesterday to study. He is someone I have known for about 6 years and we have always been friends, but the last 2 - 3 months he has become really touchy. Always finding excuses to put his arm around me or give me a hug. I have tried t be polite and reinforced my boundaries several times, to no avail. <br>So, I usually sit on the floor to study because I find the couch has too much texture for me to be able to focus. My desk I have upstairs so I only go up there if I need to print something. I was sitting on the floor at my coffee table and he came behind me and started rubbing my shoulders and arms. This has happened before so I was expecting it, but this time, he slipped his hands down to the front of my sweater and cupped both of my breasts. I froze because I was so shocked someone would do something like this without asking me. After he did this, he quickly put his hands back on my shoulders. I stood up and turned to him and asked him what he was thinking with a very angry tone and he said he thought I would like it. I asked him if he had ever asked me if I wanted to be touched like that and he admitted he hadn't but told me he thought I would like it. I asked him to leave and I called a taxi for him. <br>I just don't understand what goes through someone's head when they touch someone like that without asking. I am so angry. <br><br>Edit: <br>Thank you to everyone who has commented on this. I didn't expect it to blow up like this but I appreciate all of the input and personal stories. He no longer has my number or any way of contacting me and I will not be answering the door if he comes to my house. <br><br>Edit 2: <br>I spoke to a campus administrator today and I have submitted a formal complaint regarding this behaviour. I am going to speak to a professor tomorrow about how to proceed and how this will affect his academic standing.