You're skipping over the Jewish testimony, like Yehoshua Gorodenchik, the Irgun physician, testifying that they had committed the war crime of killing prisoners.

And you have no good explanation for why Lehi members would lie about what they saw their comrades-in-arms do:

"LHI members tell of the barbaric behavior of the IZL toward the prisoners and the dead. They also relate that the IZL men raped a number of Arab girls and murdered them afterward