Research has shown that witnesses usually don't tell the truth, either because they are too shocked by what happened or they are member of the group which has an interest in any of the outcomes.
Yes, true, sometimes, as illustrated by the ridiculous stories told by many 'holocaust survivors'...Most of their testimony was given many years after WWII, and many were paid....Tales of 'gas chambers'...The supposed existence of gas chambers was never noted by Eisenhower, Churchill, any war leaders or military, or any journalists after WWII, which is notable, since the existence of such 'gas chambers' would have been world wide news, and certainly been brought to the docket as a war crime at Nuremberg....Most of the gas chamber nonsense was 'Made in the Soviet Union', or hatched up by worms such as Elie Wiesel.
In this case, the ex-Marine gave completely reasonable testimony corroborated by other passengers on the ship, and his testimony was given only a short time after the Israeli attack, so 'embellishments' of history could not be spread so easily by controlled media.
This goes hand-in-hand with the atrocities committed by Israel against the Gaza population in 'Operation Cast Lead', which has been thoroughly documented by a myriad of media sources.