So is it considered rude to talk about other food while you're eating your current food? I don't think the pheasant you're eating right now would appreciate you going on about the chicken you had last Tuesday. Show some respect, people! And if your food is poorly prepared... avoid saying things like, "This is the worst veal I've ever tasted!" Somewhere a baby cow would probably be crying. (Again.)
And just for the record... I think this only goes for animals. Fish are even questionable but I'll include them just because I'm feeling generous right now. If you're a dead potato and you're reading this... I mean, come on. You're a potato. What did you expect?