A civil rights organization says in a new report that the National Alliance, once one of the nation’s most powerful white supremacist groups, has virtually collapsed under the decade-long leadership of North Royalton resident Erich Gliebe. The report, posted online today by the Southern Poverty Law Center, says the National Alliance has “become the joke of the neo-Nazi movement.” The law center, a Montgomery, Ala., organization that monitors hate groups, says alliance membership has fallen from 1,400 a decade ago to about 75 — “a tiny band of small-time propagandists, criminal thugs and attention-seeking losers.” Gliebe, 49, took over the National Alliance after leader William Pierce, author of the 1978 race-war novel “The Turner Diaries”, died in 2002. Pierce, a former physics professor, led the alliance since the early 1970’s and had a large following in the United States and Europe. Since his death, the group has been splintered by internal revolts and failed leadership, said Mark Potok, editor in chief of Southern Poverty Law Center publications, who wrote the report. “Gliebe’s extremely poor leadership and lack of charisma have dramatically led to the decline of the National Alliance,” Potok said in an interview.