I see the copyright issue as a valid one. If copyrighted images are being used inappropriately in the userboxes, then certainly the images should be removed.
Having said that...the vitriol I've seen expressed regarding userboxes seems to go above and beyond a concern for copyright laws. Barring a server issue, I have to ask, what's the fuss? Most of the arguments against them seem to boil down to "I don't like them, so, rather than just not have them on my own userpage, I don't want them on anyone else's either."
This whole thing reminds me of H. L. Mencken's joke about the definition of a Puritan: a person who is worried that someone, somewhere, someplace is having fun.
Joyous