Any Scouting parent opposing gay scoutmasters is vulnerable in cities with a sizable gay population.
If a parent takes a leadership role in opposing gay scooutmasters, it is fairly easy for opposing pro-gay elements to make trouble for them. All it takes is discovering where they work (pretty easy, since you usually have your office number listed in your kid's file as an emergency contact number), and then finding some gay people to notify in your company, who will then complain to HR about "this homophobe" creating a "hostile work environment".
By this means, it's fairly straightforward to silence the opposition
But do they not need real grounds to register such a complaint? Or do you think most companies consider support of the BSA on this to be such grounds?