What does John 7:51 mean?

Despite the understandable stereotype, not all Pharisees were blatant hypocrites or irrational egotists. Nicodemus lives out concepts such as education, reason, and morality, even when investigating someone so critical of his sect, like Jesus (John 3:1–2). The reason Pharisees were so respected, in fact, was specifically because they were generally intelligent, moral, educated men. However, the other Pharisees have already made up their minds to have Jesus killed (John 5:18). They respond with rage when the men they sent to arrest Jesus comment on His amazing words (John 7:46). All Nicodemus has suggested, at this stage, is that his fellow experts in the law follow the law: which explicitly says that Jesus is owed due process (Exodus 23:1; Deuteronomy 1:16–17; Proverbs 18:13). In other words, the code Pharisees claim to live by demands Jesus be given a hearing, not immediate condemnation.

Sadly, Nicodemus' associates, are so blindly enraged by Jesus that they reject this suggestion out of hand. In the next verse, they will not only ignore Nicodemus' request, they will insult him by suggesting that he is backwards and low-class, like the Galilean Jesus. And they will issue a challenge which is ironically mistaken.