You do know that what you said is pretty contradictory? I see your point, but your argument for killing livestock is pretty silly (not that I'm against it). Judging by what you said it's ok to kill people too, because they by no means are endangered from extinction. Pigs role in their own filth? Humans pollute the Earth.
I agree with your last paragraph though.
The main argument for killing live stock, is it feeds billions of humans, doesn't damage their numbers, and they are not intelligent animals. They are nutritional and healthy for us to eat also and are an ingrained part of the human diet. Whale meat is not. The massive amounts of mercury that reside in Whales actually kills humans if enough is ingested.
It isn't a contradiction at all, it would be if I valued a human life on the same level as a chickens life.
The pig comment wasn't meant to be taken as an actual reason to kill them. It was a silly comment that's only purpose was to underline that Pigs are not intelligent on the same level as Dolphins, Whales, or Chimps. Not that rolling in your own filth is actually a sign of lack of intelligence. But it certainly isn't a sign of one either.
The fact that humans are destroying this planet, where other sentient intelligent beings like Whales are not, means to me they deserve our help to survive rather than just another species that humanity has raped.