The Boy Scouts of America, an organization once known mainly for welcoming boys to a world of adventure, self-sufficiency and good citizenship, now is more famous for the groups of people it bans: atheists, agnostics and homosexuals.

It’s been a sad evolution and an unnecessary one. The Girl Scouts, as well as international Scouting organizations, have carried out their similar missions without resorting to intolerance. By refusing once again this week to admit gay people to its ranks, either as Scouts or leaders, the Boy Scouts may have satisfied some of the religious organizations that sponsor many of its troops, but it risks long-term irrelevance. Participation in its traditional Scouting programs has steadily declined over the last decade, by more than 15 percent, and is down more than 40 percent from the early 1970s. Some may believe that by banning people who are openly gay, the organization is keeping out sexual predators. But repeated studies have shown how false this assertion is. Besides, if that were the reason, what would be the point of prohibiting a lesbian woman from being a den mother, as the Boy Scouts have done?

Yet as society grows more accepting of homosexuality, and less willing to overlook discrimination based on sexual orientation, the Boy Scouts will feel increased pressure to become a more tolerant organization. Support from corporations and municipalities might be harder to come by if it doesn’t change its policies. The organization’s marketing logo reads “Prepared. For Life.” Unspoken but increasingly obvious are the added words “but only for some.”