I come into contact with too many things I can't control that may or may not be dangerous. I think meat is dangerous enough to warrant not eating it at all. As it happens, I also think that the meat industry is extremely hard on our environment. This is enough to keep me away from meat forever.
If one likes animals at all, I think that beef is easy to give up. While I admit that all of my favorite meat products came from a cow or a pig, cows are cute, dammit, and pigs are finer creatures than they are given credit for. Of course, now that cows are fed chicken manure instead of a pure corn or grass diet, I suspect they don't taste anything like they used to. And what they do to chicken...yuck. With all that E. Coli rampant in their feed, one has to cook the hell out of beef these days, and that's not how I ate the stuff anyway.
Once upon a time I used to like shellfish. Then my father pointed out to me that shellfish are merely insects that live underwater. That pretty well grossed me out, but then I started giving some thought to where they live and what *they* eat, and that was the end of that. Fish was the last thing to go. I didn't eat much of it to begin with, so that was no great loss. For my reasons, see the meat link or read Neal Stephenson's Zodiac. It's kind of a shame because Maryland is so proud of their seafood. I'm sure it's better than anything I might have eaten in the Midwest. Heck, I think they kick you out of Maryland if you're not salty enough. Maryland is unfortunately not immune to problems with sick fish in their waters. The Pocomoke River was closed for part of the summer due to pfiesteria killing the fish.