I don´t know. Violating kashrus and not washing the hands before eating violate The Law which Jesus claims to have supported.
Jesus' answer to the charge is found in vs 3.
Mat 15:2 Why do thy disciples transgress the tradition of the elders? for they wash not their hands when they eat bread. Mat 15:3 But he answered and said unto them, Why do ye also transgress the commandment of God by your tradition?
One commentary says this: "The tradition they transgress is but man's, and is itself the occasion of heavy transgression, undermining the authority of God's law."
Even the pharisees admitted it was not God's law but "tradition of the elders". But they were imposing it as equal with God's law. In fact, the Mathew Henry commentary has a quote of a Rabbi equating it with adultery.
Jesus turns it around on them, and uses it an an opportunity to point to other "traditions of men" that were undermining God's law, including the way the pharisees were avoiding honoring their parents.
This commentary does a pretty good explanation. David Guzik Commentary
Mathew Henry's commentary has a lengthy and deeper explanation. Mathew Henry Commentary - Matt 15