I am not a big cat person, so maybe I am wrong, but I think why cat mixes are "flamed" in the same way dogs are is becuase the breeds are less recognizable outside the show world. Most people on the street can recognize and name several dogs breeds...poodles, labs, golden retrivers, etc. But ask those sample people to name cat breeds, and could they? I couldn't!
Cat shows aren't televised the way Westminster is, and do see cat sports on TV, so I think ingeneral the breeds are less recognized.