He questioned the injustices that were structurally incorporated into the system. He picked his battles carefully, but fought them with unparallelled commitment. However, there is plenty that Dr. King was unable to question within the context that he worked in.
Today he is one of only three men in the US who have been honored with a national holiday. The other two, Christopher Columbus and George Washington, were both slave owners who, in their context, served this country just as well.
It is our duty as responsible citizens to question the injustices in our system as we become aware of them. We must remember that we are part of an ever-changing world. After all, each of these men worked within a common church, to please the same god.