Historical accounts of Prophet Muhammed describe in detail his clear and fair dealings with the Jewish tribes in and around the city of Madina.
As soon as the Prophet emigrated to Madina, he established the Constitution of Madina or ‘Sahifa’. It was the first multicultural, multi-religion constitution in the world that gave everyone equal rights, including the Jews. It gave legal autonomy and the right to practice one’s own religion freely. It required a commitment to defend the city of Madina against external aggression.
The Prophet upheld both the letter and spirit of this agreement. Even non-Muslim scholars, such as Montgomery Watts, never mention that the Prophet betrayed his agreements. In fact, it was the other way around; other parties committed acts that were contrary to the agreement. This occurred on more than one occasion. Penalty was imposed but only to the specific group of people who committed the offense. Had it been applied to all, one could suspect group bias, such as anti-Semitism. However, that was not the case.
Furthermore, the punishment was always proportionate to the offense that was committed. Uncovering a Muslim woman was different to conspiring to kill the Prophet, and such actions were handled in different manners.
The ultimate betrayal occurred in the Battle of the Trench, when a group of Jews from Madina contacted the enemy, renounced the constitution of Madinah, and helped the enemy during war against Madinah. In modern times, this is referred to as high treason at the time of war.
Penalty was imposed but it was not the Prophet’s sentence. The people of Banu Quraiza had their own arbitrator. He ruled according to the law of the Torah, which specifies killing of men for treason. The Prophet simply agreed with his sentence. To say that the Prophet massacred Jews is therefore a distortion of historical facts.