That is a totally asinine statement, unless you are able to explain why Israel would do so for no reason whatsoever.
"Being able to get away" with it only works in the muslim or banana-republic (Argentinian) mind...
It also works with McNamara's mind, it would seem.
But I say that rendering no opinion on the attack itself. What utterly disgusts me is the statement attributed to McNamara, with equal disdain for LBJ unless McNamara was making it up as he went. Whether it was an accident or on purpose, calling back our rescue mission was inexcusable. Heck, even if we were ready to write off the USS Liberty, it wouldn't have hurt to take out the torpedo boats as a "don't ever let it happen again" message. That wouldn't have given away NSA's capabilities.
Okay, doofus, I'll spell it out from you. Israel, for whatever reason they attacked the ship, knew they could get away with it because they knew the US would never relatiate militarily against them. The fact that no retaliation happened shows they gambled correctly.
I've read no good excuse for the attack, and those trying to excuse it usually end up trying to flash the anti-semite card, which means even they know they can't justify it.