What does John 7:50 mean?

It's easy to create unfair stereotypes in our minds, and those are still unfair, even in a context which heavily reinforces them. In the case of the Pharisees, modern minds tend to leap directly to concepts like "judgmental," "hypocritical," "arrogant," and "rigid." Certainly, those were legitimate criticisms of many Pharisees, as mentioned by Jesus Himself. And yet, in Jesus' era, the Pharisees were also known for being extremely moral, highly educated, and eminently respectable men. Nicodemus is an example of how that combination of intellect and conviction is meant to operate. Unfortunately, it earns him insults and ridicule from his peers when it comes to Jesus.

The Pharisees are in the midst of a fit of rage over Jesus, and the failure of their officials to arrest Him. Their primary point of evidence against Jesus is pure pride: "He does not agree with us, so He must be wrong." Nicodemus has visited Jesus in the past to investigate His claims, in a reasonable and respectful way (John 3:1–2). Here, all Nicodemus suggests is that the Pharisees give Jesus due process—to fully hear Him out before dismissing Him as wrong.

In response, his fellow Pharisees will not only continue to display arrogance, they will insult Nicodemus with an ethnic remark, and then make an ironically ignorant challenge about Scripture (John 7:52).