Attacks on neoconservatives aren’t automatically antisemitic, but there often IS an element of antisemitism in the attacks- particularly in attacks coming from the “paleoconservatives.”
If you’re not familiar with the term, well, that suggests you’re one of those who thinks “the right wing” is a monolith. In reality, the conservative “movement” has a lot of factions, many of which don’t much like each other. They may rally around some of the same candidates, but there’s often a lot of tension and mutual disdain. Anyone who reads leading conservative journals has observed this.
A Pat Buchanan (paleoconservative) and a Charles Krauthammer (neo) both embrace Ronald Reagan, but for very different reasons. To people like Buchanan, Reagan represented an attempt to reverse the dominant trends in American society and return to a better past. To people like Krauthammer, Reagan represented a resurgence of American power, which could be used to change the rest of the world for the better.
To the paleoconservative, the outside world is ugly and evil, and should be shunned. That’s why, all these years later, you’ll still hear Pat Buchanan using the slogan “America First.” To the paleo, the Middle East is a hellhole we should have nothing to do with. To the neo, the rest of the world must be engaged and dealt with, and (ideally) brought around to America’s values.
So, you have two sizable groups of “conservatives” with diametrically opposed views of America’s place in the world. Tension is inevitable. And this tension is aggravated by religion and ethnicity. Almost all the paleos are Christians who are far more interested in domestic social issues than in foreign affairs. Almost all the leading neos are secular Jews who don’t much care about combatting abortion or homosexuality.
So, when a paleo attacks policies advocated by neos, he’s just liable to betray some hostility toward Jews as a whole, and not just toward the individual neos. Pat Buchanan thinks the U.S. should completely wash his hands of the Middle East, which he thinks will always be a powderkeg. And when he sees Jews neocons advocating a hawkish policy in the Middle East, he’s predisposed to think they’re acting in Israel’s best interests, not America’s. Thus, his rhetoric (and that of his comrades on the far right) increasingly shows a hostility toward Jews.
So, in answer to the OP: there is DEFINITELY an element of antisemitism in some attacks on neoconservatives. Obviously, one can disagree with the neos on a host of issues for perfectly valid reasons. But if the neocons suspect there’s SOME antisemitism in the attacks on them, they’re correct.