The people called for Jesus to be crucified.. but that was not the entire population of Jews in Israel.. Pilate asking such a question was all part of a plot, that of the Roman government and the Temple authorities. They both feared His growing popularity, while some called him Messiah others called Him King of the Jews while others called him Rabbi...So first the High Priest and Sadducees had to insite the worshippers, then the plot thickened from there.. The high priest insinuated that Jesus was a heretic and blasphemer.. so when Pilate asked which man was to be crucified, which was worse a thief or a blaspheming heretic? Well that left no doubt in their minds.. Although to a Roman this was not exactly a punishable offense and thus he washed his hands and to his glee thinking he has stopped the preaching and teaching of this man and surely he had stopped his followers,and for sure the Jews would all go back to business as usual and the Romans would indeed continue to control the region..