I agree that you should try to find the best home possible. Barring that, I think a quick humane end would be preferable to cock-fighting. The reason I don't hatch is that I don't want to worry about too many roosters and drakes. I already have too many (natch-not enough hens LOL) from rescuing some wonderful boys from a possible stew pot fate. But I don't eat birds at all-too much like eating my friends!
I just sold some of my sheep today as I did not have enough pasture to support some unexpected lambs that came last spring. Although I clearly posted in my Craigslist ad that I was not selling them for eating, people still asked me how they were for meat. I am buying an emu next month from somebody who had the same thing happen when she posted on Craigslist. Oh well, at least people asked up front, instead of pretending they were going to pet homes.
If you have time to be extra particular, you could always ask the buyer if you can come visit. That may vet out some folks with other intentions. True you don't have rights after the animal is passed on, but you could make that a condition of the sale.