Great points NavyHoops!
Academy grads are an easy target. It's like saying "tax the rich." Who's going to defend those good-for-nothing silver spoon endowed nancy pantses?
Part of it is, once you have a common point of entry, it's easy to point to it and say "SEE!"
It's hard to do that with ROTC.... "he's horrible because he's ROTC..." OK maybe at UT but not at Vandy, not at UNC Chapel Hill, but maybe at Auburn. Painting prior enlisted officers with a broad brush just hurts some enlisted members ideas of what it means to be enlisted. "He's horrible." OK, but he came from the same source that you came from.... so what's that say about you?"
There's also an expectation that you'll do well, but some will just wait for you to slip up and say "see, it's an academy thing."
As with most things, one or two bad apples can make everyone else look bad, but having such a large officer population coming from one commissioning source aids in the finger pointing.
I'm not sure if it's worse or better in the Coast Guard. About 40% of the officer population in the Coast Guard came from USCGA, so we weren't as "rare" (at least within the service, which is also small). I think where I saw (and see) it more often in the Coast Guard, is not from the enlisted, but from other officers. The USCGA community is relatively tight, and whether we like it or not, CGA officers know each other from schools and assignments. OCS or direct commission officers don't have that connection, and I don't think that makes all of them happy. You can't let it get to you though. It's their problem not yours (unless you are infact a problem).