Try to look at it from his perspective. You meet a new person, get along really awesomely, are really open and comfortable with each other - even become best friends.

Then, this person says they actually like you romantically. You don't return those feelings. You're a bit unsure - maybe they were never really interested in your friendship, and you probably wouldn't have been so open and comfortable if you'd known - but you understand that sometimes close friendships can spill overy into romantic attraction so you feel okay about it.

Then, as soon as your "best friend" finds out you have nothing to offer them but your friendship, they are GONE. Literally avoiding you for weeks. Just as you're going through domething pretty intense, the best friend you would have turned to is yanked away. You have been 100% honest about your intentions, they have not, and somehow it feels like you'require being punished.

...so while you're totally right to do what you need to do for your mental health and sanity, it really does suck when a close friend decides to burn the friendship because you don't want to sleep with them, especially if (acording to him) there was no basis for assuming it was mutual.