In Justice Stevens dissenting opinion in Boy Scouts of America v. Dale
he noted that the BSA's ban on gays did not stem from any of the principles taught in the Scouting Handbook. Even in the Scoutmasters Guidebook the Scoutmasters are instructed to defer these teachings to the child's home, religious leaders, doctors, or teachers. In the list reiterated by Justice Stevens Scoutmasters show up as the very last, and they are told to only answer at their comfort levels.
As is par for the course with the Mormon church their societal views have changed with convenience. In 2008 they broke the separation which they had maintained with staying out of political measures to intervene in California's Proposition 8; four years later they are now changing their teachings from "it's a lifestyle choice", to "you might be born with it but it's still a choice." There was a similar turnaround, although much more dramatic, in 1978 after the civil rights movement was well past and the rest of society had moved forward, leaders of this relatively small church changed their policy after much pressure from the government and other groups. Up until that time church members were taught that the "negroes are not equal with other races" (Bruce R McConkie, Mormon Doctrine, 1966, pp. 527-528)
The new policy which the BSA has put forth reflects the protocol portrayed by the Mormon church on tolerating homosexuals in their wards (a ward is a local Mormon congregation). As stated on the Mormons and Gays website:
Members of the Church who have same-sex attractions, but don't act on them, can continue to enjoy full fellowship in the church, which includes holding the priesthood, carrying out callings, and attending the temple. Unlike in times past, the Church does not necessarily advise those with same-sex attraction to marry those of the opposite sex. Same-sex attraction itself is not a sin, but yielding to it is.This is similar to the stance which the BSA now has that the scout can be gay, but cannot act on it. The BSA reasoning goes equally with all scouts because of their stance against premarital sex. What differs right now is what happens when they are adults: in the Mormon church they still cannot act on them; in the BSA they aren't allowed even if they don't act.
As there has been an evolution of man throughout the ages, from our distant ancestors who we share with chimpanzees, to our neanderthal cousins, so there is an evolution in society, and in our morals; this evolution has continually been towards the equal treatment of our fellow man, even to an extension of this to all our brothers, sisters, and cousins found throughout the flora and fauna on the Earth. We may continue to look forward to a day where unequal and discriminatory policies are not found within civilization, and the solidarity of all things here on Earth can be felt through the realization and recognition of our common genealogy.
Picture By Douglas Muth from Ardmore, PA, USA (My old Boy Scout merit badges) [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons