Boy Scouts of America is a private organization and as such has the right to set requirements for membership. The Scout Law explicitly states that a scout is reverent. The Scout Oath states that a scout will "do my duty to God and my country." You can see how an atheist could not recite the Scout Law or the Oath with a clear conscious. The only way atheists could participate in Scouting would be if BSA changed the Law and the Oath, but neither of those things have changed since their adoption in 1911. To change them would be to compromise the principles on which Scouting was founded.
As far as pushing Mormonism, this is the first I've ever heard of it. I am an Eagle Scout and have been very active in the Scouting community for the last 20 years or so. While Scouting makes a big deal about being reverent, they do not push any specific denomination. There are no religious requirements for advancement through the ranks. My troop was filled with a hodgepodge of Baptists, Methodists, Catholics and a few others. Scout camp chapels were all non-denominational (though a few of the larger camps had chapels by denomination) and very general.
There was no religious agenda being pushed upon any of us.
As far as the gays issue, would you want your daughter going on an overnight girlscout trip led by a male leader? Its the same issue. I know most gays are good people who wouldn't harm anyone, but don't pretend they are all saints. There is, at the very least, a perception issue and at the worst there is a legitimate safety issue for the boys in the troop.
BSA is a great organization that does a lot for boys and for this country. Every Eagle Scout has to do a service project that benefits his community. These are no small things, they typically require a few hundred man hours and get the scout's whole troop involved. They can't be done for Scouts or on Scout owned land. Every boy, to advance in the higher ranks, must hold a leadership position in the troop for at least 3 months. They learn how to work together, how to plan a camping trip, how to prepare for emergencies, basic first aid. Many boys have found their vocation through merit badges such as Environmental Science, Radio, Emergency Preparedness, Music or even Computers.
You can disagree with BSA's morals or with their admissions requirements or whatever. But please, don't demonize an organization that has done so much good and that is well within its rights to determine these policies you find disagreeable.