I actually don't believe in any prophets, but I do find the scriptures (Whether they be Tanakh, gospels, Qur'an) to be interesting myths, legends, folklore, parables or allegories, semi-historical accounts, etc, but it doesn't mean I have to believe in them to be true.
What I see in Muhammad's life from biographers and historians, is a one-sided propaganda. It seemed that everyone is at fault, but not Muhammad's or the Muslims' faults.
They can't provide sources for the other side or from independent sources.
And the utter BS propaganda, about the Banu Qurayza asking for a Muslim-converted Jew to pass judgment on them, is nothing but a biased Muslim would write about, so that Muhammad doesn't stain his hands with blood. He allowed for the beheading to take place, so is he any better than any terrorist acting today, when these terrorists behead their victims?
No. They are just following what their prophet has done, since Muhammad is their role-model, so it is ok to behead enemies in time of wars.
I don't see any difference to what Muhammad have done to Banu Qurayza to what ISIS is doing in Iraq. Murder is murder, and genocide is genocide, but making excuses that it is not or that it is the other side is at fault, is nothing more than hypocrisy and condoning murder.