Most cancers only happen to meat-eaters.
I can tell you for a fact, this isn't true. The only cancer this applies to is colon or intenstinal cancer (mainly to red meat eaters who don't get enough fiber). And that's only because the waste hangs out there so long it can possiblly turn cancerous.

However, people who eat meat can have a host of other problems though. There are possible heart problems for red meat eaters. For all you people who like chicken, science still isn't sure of the long term effects of the hormones the chickens get pumped with. Open water fish are subject to pollution. Farmed fish are subject to whatever chemicals are put into their food. All in all though, fish are probably the lesser of the "evils". Then again, some of the alternatives aren't that healthy either. Many types of vegetarian diets include the use of beans as a source of protein. Unless you want spend an hour or so soaking dry beans prior to cooking, most people would buy canned beans (I'm loyal to Goya myself ). In that case, you have to worry about whatever preservatives are used to maintain color and consistency. I'd have to check this, but for all I know, dry beans have preservatives too...

I've said it before, veganism is the Diet of the Future.
This is a little over the top.