Never met a freegan who ate meat, either. I think it's more of an acknowledgement of where your money is going than what you are wearing. If you find a good pair of Adidas shoes in the dumpster, none of your money is going to support what you consider to a cruelty-based industry, so why not wear them? It's a fairly interesting way to live off the inherent wastefulness and wealth of modern American culture, without monetarily supporting companies you consider "immoral." Never had a problem with the Freegans, especially since they taught me everything I know about dumpster-diving. You can eat pretty well just from dumpster-diving if you're resourceful enough. I knnow this shocks some people, but it's really a matter of societal conditioning and what you're used to, more than dumpster-divers doing anything "wrong." Think about it.
As long as you go to the grocery store and college campus dumpsters, and don't eat the hepatitis-laden Big Macs, you can do pretty well...