For years I believed the Israeli's intentially attacked the Liberty. A few years ago I did a review of the various articles on the web about it and decided that in fact it probably was an accident, but with a lot of evidence to suggest that it wasn't.
The problem with the attack was that it was a military SNAFU on a high level. To rephrase the (very exhaustive and well-documented) report on what happened in AZURE magazine (not available off-line or in English, I am afraid) it is true that--due to reconnesaince information, etc.--the israeli high command SHOULD have known that the ship was American, and COULD have known it.
But--and this is the key point--they DIDN'T know it, for reasons of miscommunications and delays between army intelligence (that gathered the radio broadcasts, etc., proving the ship was American), the high command (which got those reports), and the air force (which sent the planes to attack). Simply put, the information that the ship was American did not reach the air force from the army intelligence until the attack was long over.
So, yes, if you consider the israeli army AS A WHOLE, I can see where the idea that it was intentional came from--"it" knew that the ship was American at time t, and "it" attacked it nevertheless at time t+1, which sure looks intentional! But the problem is, this assumes perfect information transfer between the branches which simply didn't exist. Yes, the army intelligence knew the ship was American at time t, and the air force attacked it at time t+1... but THE AIR FORCE DIDN'T KNOW IT WAS AMERICAN UNTIL T+2, SO IT ATTACKED THE LIBERTY WITHOUT KNOWING IT WAS AMERICAN, EVEN IF OTHERS IN THE ARMED FORCES DID.
That's all there is to it, really, except for one other distatsteful fact. The idea that israel, in the midst of a war of survival on three fronts, would deliverately attacks a ship of its only ally in the world is, shall we say, rather odd. Not logically impossible... but surely requiring a LOT of proof. It is highly revealing that some people are willing to jump to conclusion about the "awful israeli guilt"--needless to say, while ignoring the literally hundreds of Americans killed by the palestinians over the years, undoubtebly deliberately. It is not looking for the truth that motivates such "jumpers"; it's just the desire to find something--ANYTHING--to smear israel with.