Extremist group activity on or near U.S. military bases is often so secret it can easily be overlooked unless investigators know how to spot it, the NAACP was told. That testimony during the annual meeting in Charlotte of the National Assn. for the Advancement of Colored People cast a shadow over earlier statements by military officials that evidence of such activity on the bases is minimal to nonexistent. The NAACP must make the issue a top priority, said Mary Peeler, former executive director of the North Carolina conference of NAACP branches. She also said NAACP branches must establish relationships with military bases nationally and help educate communities about skinheads and white supremacists.