Yeah kind of like the tea party.Good catch, but it's mostly beyond the point. Almost all organizations have rules in place to preserve the goals and character of the organization in order to prevent a highjacking from occurring. This was a favorite tactic of American Communist back in the 20-50s. They'd join an organization, scope it out, then they'd organize a mass enrollment where they constituted a majority of the members, call for elections, vote themselves into office, subvert the mission of the organization and reorient it towards some Communist mission and they'd deplete the resources of the organization and then abandon it.
I'm pretty sure that the NAACP has some provision in its charter to prevent the KKK from mass enrolling, taking over the NAACP and then spending the NAACP resources on KKK propaganda.
Christian groups on college campuses often admit people who are not Christian but who are curious or working towards adopting the faith. Same with Muslim groups, same with Mormon groups. What they object to, and what college administrator push on them, is to allow such people to lead groups and to change the mission of the group to be more inclusive.
The NAACP is not race-inclusive in its mission even though it admits some token whites either as spectacles, as supporters of the mission, or as some form of observer.