This must really be an "hate meateater site". Your choice of words ("slave master" as an example) indicate what "kind" of person you are. But that's your choice! However, the world would be nicer to live in with less hatred.
I'm brought up on a farm and my father is still breading sheep, nowdays only for keeping the meadows open. In Sweden we have gowernment programs supporting people (like my father) to have animals for that reason. So I have seen the real animals. We even slaughter them ourselves out on the farm, and the sheep doesn't show any sign of that they know what's coming.
The stress in a slaughterhouse is (in my opinion) not from the slaughter, but more from a bad and stressed surrounding. Maybe you (there you come from) have bad "slaughterhouses". I think that you need to have a good legislation around an activity like that. I don't know form there you got that the animals get stressed because they smell blod? Have you asked them?
Sheep is an good example on an animal that need to be slaughtered then it's getting older, or do you think we should have nursing homes and retirement homes for old animals? If so, I think that you is sick. That is unnatural if anything is unnatural. Out in the nature older animals either; starve to death, get sick (without any treatment) and die, or are taken by other animals (murdered. What a shame??? Why don't forbid animals to kill each other?). The nature is not always nice and friendly!
One other example are "our moose hunting", there even the government hunt down mooses. There isn't any natural enemies (for the mooses) left, and they bread so heavily so we need to hunt them down (the hunt is around three weeks every year). This in order to keep the number on a level that doesn't give massive starvation and sickness amoung the moosepopulation. We have had problems like that. We are now trying to bread up a population of wolves partly to get the nature back in balance. Because of this "problem" we eat alot of moose-meat hear.
I can however agree with you that vegetarians (as a group) tends to be healthier than all-eaters. But is it really because of a vegeterian diet or is it because of an healthier lifestyle overall? Many meat-eaters (not all) have unhealthier lifestile, with more fat in the food, and with less exercise (compared with vegetarians). At least that is what my schoolbook in nutrition says... You have much more people suffering of obesity among meateaters. (And is not the meat itselves that make people fat.)
And for your statement about my "plants feel pain" argument (I did not say that plants felt pain, but that they were alive. And according to my biology they are.): "no brain, no pain", I would like to say that dead animals (including humans) doesn't feel any pain either.