Woe unto you, lawyers for ye have taken away the key of knowledge: ye entered not in yourselves, and them that were entering in ye hindered.

Jesus is speaking to Pharisees when he makes this statement.  I don't think he intended this to be a condemnation of lawyers in general, but of the class of people who were in power and pretended to be religious, but did everything they could to suppress real religion.  The expression "key of knowledge" is very Gnostic.  Jesus is obviously not talking about common knowledge, but a special spiritual knowledge, Gnosis.