No, there's no excuse for comparing Israel with 'apartheid'
Slate's Dave Weigel offers an argument in defense of Chuck Hagel's alleged remarks in 2010 suggesting that Israel could become an apartheid state if it did not make peace with the Palestinians: Defense Minister Ehud Barak said the same thing that same year.
As I've noted before, that was the dumbest thing Barak has ever said--firstly because it's not true, and second because it props up one of the most malicious anti-Israel memes.
Here, Weigel appears to be using a version of the argument described by Alan Dershowitz as "argument by ethnic identity"--i.e. if an Israeli said it, it must be OK. Granted, the Israeli in question was a prominent one, though Barak himself was, in his time as prime minister, accused unfairly of "apartheid" for promoting the idea that a two-state solution was preferable because it would separate Israelis from Palestinians. The term has been abused, both in the U.S. and Israel, to inflame the debate. It's highly worrisome that Hagel used it, especially after the calamity that was Jimmy Carter's Palestine Peace not Apartheid (2007).
I would compare Barak's use of the term "apartheid" to Hagel's tolerance for the term "bully" when used by a caller to refer to America on Al-Jazeera. Barak's use of the term is not a defense for anti-Israel views, any more than Hagel's tacit acceptance of "bully" ought to provide cover for anti-American views.