Anyone who thinks of another as "jew-boy communist" is clearly an anti-Semite.
So, if someone uses the term "neocon," do you think they are an anti-Semite?
Not necessarily. However, I happen to think that Pat Buchanan -- whose opposition to "neo-cons" has a long history -- is in fact an anti-semite.
And I think those who tend to use "neo-con," as a perjorative tend also to be anti-Israel, though that does not necessarily equate to anti-semitism. But there does seem often to be a "Jewish Cabal" element to their complaints.
For an interesting take, much better stated than mine, see this article about the supposed Jewish Neo-con Trotskyites (about whom Ron Paul had so much to say, the other day).