I wonder, if part of what's wrong with the dating world these days is our incessant need to put labels on everything. I'll admit that when I see a person on a dating site say that they're looking for "friendship," I roll my eyes a bit.
What made these men think that there was a natural progression from platonic friendship to future romantic coupling? What happened to the mutual commitment to the values and benefits of a successful platonic relationship?
You don't have to tell your friend that you're not interested in dating -- he already knows. My guess is he's not going to be happy with the status quo. Once the cat is out of the bag, it is very difficult to put him back in.