I'm a straight male and my best friend of 10 years just came out and told me he absolutely loves me. I'm at a loss for what to do.

I am at a loss of words. My best friend, someone I considered my brother, just came out and told me he loves me. It wasn't even a "i think we should date" he is full on admitting to being obsessed with me. To the point that he told me he is seeing a therapist to "get rid of these thoughts".He is fully aware that I am straight, in a very serious committed relationship with my girlfriend. But he only sees it as a obstical. He went into this fully expecting a different response than what I gave him.I flat out told him "look man, I really like you as a friend, but this isnt something that would ever, ever work.". I made it abundantly clear that I am straight, and have no intention of playing for the other team. Even if I was gay, he isn't even my type, and i've never even considered dating him.It hit him hard, so hard that he has made the decision to cut me out of his life. He claims its only temporary, and that the therapist should be able to help him. At this point in time he removed all contact with me, and has asked me to disappear.I basically told him I fully respect him, and would do what ever would help him in this challenging situation. As of now I am respecting his wishes and have broke contact with him.But I don't want to lose my best friend. I really do like our time together, and will really miss it if he truly disappears on me. I also fear his is emphasizing having a therapist "fix him" is only going to hurt him in the end, and he will never truly discover who is really is.I'm so lost....