The whole idea of it being required as a condition for god's forgiveness is ridiculous. A higher power needing a blood sacrifice? A supposedly all knowing, all loving god, at that? Preposterous.
It actually makes more sense that they felt justified, as Christ's ideas were a threat to the status quo, and the people were getting restless. At the time, that is how you kept the peace. Wrong by today's standards, of course.
To be honest, given that it seems that it was the crucifixion that galvanized the people in their dedication to change over time, it was likely the worst thing that they could have done.
Of course I don't morally agree with crucifixion, but back in those times it would have been justified if he was not the son of God. There had been many false prophets and once they would get as many followers as Jesus had the government leaders had them killed in order to maintain control.
Under no perspective could the crucifixion be considered a just one, He broke no Roman law. Pilot bent to the pressure of Jewish Rabbi that he had the authority to ignore. Jesus caused no unrest with the Roman Government, and even discouraged the use of the sword to up rise against whenever asked.