I can't see how raising mutt chickens is hurting the hobby. After all, if you breed a lot of mongrels and nobody wants them, they get killed and put into the freezer, which makes them useful. It's not like breeding mongrel dogs where when nobody wants them, they get turned loose to kill livestock, or they go to the pound to be put to sleep and their bodies tossed into the dump, all at rather large cost to the general tax paying public.
[[[.......It is rude to do it in a way that disdains anyone who doesn't agree and call them stupid......]]]]
We have absolutely no idea what that person said. All we've got is the OP's interpretation of what that person said, and since the OP appears to enjoy drama and a bit of righteous indignation, I suspect that what was said has been slightly colored. It certainly wasn't a direct quote. It's hard to judge what was said without having any idea of what was actually said.
I wouldn't mind having more people get interested in preserving the separate pure breeds of chicken, but if someone wants mutts, it isn't hurting me in the least. Not to mention that anyone who doesn't see the point of maintaining pure breeds isn't going to be a good steward for the breed, anyway.