The National Organization for Marriage is in violation of 501(c)4 tax exempt laws which require that to have the tax exempt status, a group must be involved mainly in "social welfare" activities, not political ones.
NOM is a PAC. It endorses and campaigns for candidates according to whether the candidates are anti-gay. NOM's activities are centered on elections and on ballot measures.
The SPLC's 2012 Intelligence Report on NOM is "National Organization for Marriage Continues Spreading Lies About Gays."
Gay tax payers should not have to subsidize anti-gay hate speech. NOM sponsors anti-gay political rallies where its chosen speakers yell through megaphones that homosexuals are "worthy to death." How does doing that get NOM classified as a "social welfare" group?