I've ordered from several different hatcheries, and MMM is one of my favorites. I know MMM is the go-to hatchery for other BYCers, too.
I think you just let their prejudices roll off your back. A bird from a breeder is a choice for some, but often is not the best choice for many people. It all depends on what you want from your chickens. For example, many birds from breeders that are bred to be show birds lay fewer eggs than hatchery birds, while a hatchery bird is unlikely to win at the show. If you just want eggs from a nice backyard bird that looks mostly like the breed you wanted, then a hatchery like MMM is just the right place for you. I'd rather order from MMM than buy at the feed store, for instance.
One thing that I've noticed is that MMM is such a large hatchery, and so many people order from them, that of course there will be problems with some orders, with DOA babies, etc. Then those problems get reported at a place like BYC and it seems like everyone has problems with them, when in reality it's only the dissatisfied people that are telling their stories and those of us that have ordered hundreds of chicks from MMM, never had a DOA (but have had a few die within three days), never had a pullet turn out to be a roo, we don't really have a story to tell so the good things about the hatchery aren't heard. If my ramble makes sense, LOL.