When I was stationed in Alaska, just about every waitress, bar tender and others with simliar jobs, did that in the winter, while simultaneously working in the fisheries or canneries and related jobs in the summer - every waitress did that. I certainly wouldn't want to work in the crab boat industry, commercial fishing and related, not due to some animal rights reason, rather because of the cold and danger involved. And I'd think that working at a cannery would be a smelly job, it must pay well, and wouldn't have any personal reasons against working at a cannery.
Despite being a manly man (?), I don't care to hunt, nor otherwise kill animals, so I wouldn't work in slaughter house. I had a friend work at a local turkey farm/factory with a smell that I wouldn't want to be around, flies everywhere, and the unseemly knowledge of what really goes on with packaging/processing turkey, poultry or other meats. For example, according to my friend, healthy, normal looking turkeys almost all become prepared whole turkeys for Thanksgiving, but any turkeys with missing limbs (missing by birth or damage) or any other feature that would look bad as a whole packaged turkey becomes turkey nuggets or similar cut pieces. This makes me believe that McDonald's chicken nuggets are made from deformed chickens. Not that that is a health issue, but the idea kind of turns the stomach.
Really, I wouldn't work in the health care industry either for similar reasons. I don't want to actively work around dying people and all the gore.
Similarly I wouldn't want to work in the industrial clothes washing industry (not just because its an extremely low paying occupation), but another friend worked at one, after high school, and bed sheets from hospital beds always included bio-hazard materials, gore, loose hypodermic needles and other risky or discomforting encounters.
I currently am a smoker, but would probably not work for a tobacco company, partly as I have no attaction to moving to the south where those jobs are and not for any other reason. The industry doesn't attract me, but I don't have any personal misgivings for those who do work in that industry.
I've worked sales in the past, in general I hated it, but I also run businesses of my own, and have absolutely no problem with selling my skills, because I'm not selling somebody else's product, I am really just selling me - my graphics skills, talents and creativity.