When Jesus sent forth the apostles “to the lost sheep of the house of Israel,” he told them certain things to beware of.
The instruction here is specific. Beware of men, in order to be careful we have to be wise. Jesus is instructing the disciples to be wise, because there are men in the world who will take advantage of your beliefs and use it against you in court. They are going to be insulted in religious places and what they preach will be ridiculed. This happened to them not too long after Jesus ascended to heaven.
We can expect that those things will happen to us at every age of this world. But we need to wise up so that we see these things coming and be able to defend what we believe. Jesus says that we are sheep in the mist of wolves. One thing we should never forget is not who we are, but who He is. He is our Shepherd.