They probably don't taste bad...I mean, most animals somewhat taste good (crocodiles, frogs, hogs, deers, pigeons, eels etc). Now, it would be utterly ineffective to try to breed cats for meat, which is IMHO why we have such a small variety of regular meat. We chose the species that were the most convenient, regardless of any other inherent ethical consideration.

So for better or worse the line is purely arbitrary, and people's pet pig being off-limit by virtue of being declared a pet is an example of that.