[fwdude]

They can always start their own scouting organization. Why don't they?

That's not ever an option for a parasite. They must invade and infect a host.

[scottjewell]

“That’s not ever an option for a parasite. They must invade and infect a host.”

This is the crux of it. And the reason why the gays won’t stop at civil unions but must invade traditional marriage; why they don’t start their own scouting organization, etc.
Not only due to their parasitic nature, but also their goal: To transform and remake society in their own image.