In the New Testament we find various rules of accommodating others in the spirit of love and peace. For example:
To the Jews I became like a Jew, to win the Jews. To those under the law I became like one under the law (though I myself am not under the law), so as to win those under the law. (1 Corinthians 9:20, NIV)
I understand this to mean that to those who considered themselves still under obligation to observe some ceremonies of the law, though they had begun to believe the Gospel, Paul became like them under the same obligations.
However, when the Pharisees pointed out that the disciples did not wash there hands before eating Jesus did not accommodate them at all, but used the opportunity to show that he was in direct opposition to traditional Rabbinism.
"Why do your disciples break the tradition of the elders? They don't wash their hands before they eat!" (Matthew 15:2, NIV)
The question is: Why was it so important to Jesus NOT to accommodate the seeming neutral rule about washing hands before eating bread? What was the harm in accommodating the Pharisees?