If that were the only motive, they wouldn't be. But I don't believe that the people pushing so hard have such pure motives.
If you want to know the answer as to why those Americans were killed, there are 2 or 3 theories that are all somewhat credible and highly detailed. Read them.
There is no way another hearing on this issue is going to answer the question with any more certainty than advanced by those theories. Knowing this, why the demand for more hearings except to harangue Israel? And why harangue Israel now over this? All the people involved are very old or dead. The relationship between our countries has changed. The people have changed. Their society and their geopolitical position has changed.
We no longer curse Japan for Pearl Harbor, why continue to curse Israel for the Liberty? We don't want Germany cursing us for Dresden, or Japan for Hiroshima and Nagasaki, or Vietnam for Mai Lai. Now that Israel has paid reparations and apologized, a very real sign of contrition, it's time to forgive. If we cannot forgive, we cannot expect forgiveness ourselves.
Nevertheless, there are those who refuse to understand this point of view and continue to press for something that is impossible to ascertain. I won't call them (all) anti-semites, but they have at least a very strange point of view with highly unrealistic expectations -- that's very suspicious in my view.
The difference is that when those others attacked they did not proclaim it to be an accident and attempt to suggest that they were our friends. They were our enemies. If Israel is guilty it should confess. If it is innocent, then it has done what is needed, or at least all that can be asked of it. Friendly fire with apologies and reparations is one thing. Cynical deceit, arrogance and treachery is another. The families of the servicemen who died that day deserve to know which of those two possibilities explain the tragedy of the Liberty.