In re-reading my post, I realized that I didn't answer the original question: Is Scouts a good foundation for a becoming Mustachian? My answer to that is I don't know, but it doesn't matter, because there are other things about Scouts that mean we don't participate. The rest of this post is off-topic, so jump off here if that doesn't interest you.
We did Scouts with our two boys for several years, because my husband was an Eagle Scout and has positive memories of it. Also, we live in the city and wanted the outdoorsy aspect for our boys. It has way more religious undertones and patriotism than we are comfortable with (and far less outdoorsy stuff than we thought), and when they re-affirmed their bias against gay leaders, we felt like we had to stop supporting the organization. I had had a conversation with a neighbor 15 years ago who is supportive of gay rights and kept her son in the scouts back then in order to "change the organization from within." Fifteen years is enough time to change from within on this issue as far as I'm concerned.
I think Scouts does a lot of good for a lot of people, but it does not align with our values and that was bothering me more and more as time went on. Aside from the gay discrimination issue, I am not for blind patriotism, and I think teaching kids any pledge falls in this camp, as they are too young to know what they are saying and to understand the issues. I try to teach my kids they have a responsibility to their family, their community, their country, and their world, but they do not owe allegiance to anybody.
I know many do not share my sentiments, so I'm not suggesting organizations like the scouts should not exist, but they are not for me.