The tea party is made up of different groups and their organization is broken up among those different groups. You don't have leaders in the tea parties, only organizers, and each member can volunteer to be an organizer. How can the tea party come out against racism within their group, if it is just an assembly of people? Some may not even be registered members of the tea party but just show up at the rally.
All large groups have some small elements of racism because racism exists among all ethnicities. Every-time I've seen a tea partier asked about racism within their group, they reply, "I have not seen any racism in the rallies I've gone to" because it is a small percentage of the group as a whole.