A sense of security knowing that your child can be left with other boys/adults and there not be any problems.
This pretty much sums up the problems I see arising from accepting homosexuals into the group.
Camping (which is much more prominent in boy scouts than cub scouts, a monthly ordeal in my troop where the adult:child ratio is around 1:3-5, as opposed to once a year in cub scouts where pretty much every cub scout has at least one parent) is in a fairly intimate setting, middle of nowhere woods for an entire weekend.
All that needs to happen once homosexuals are openly admitted is a SINGLE pedophilia case to go down or a sexual harassment claim between scouts and then shit will undoubtedly hit the fan; parents screaming "This would've never happened if we never accepted gays in the first place", and the LGBT community + supporters saying that this is an n=1 case yadda yadda yadda. The end result being back and forth with no progress.
Not to mention the fact that it'll be VERY hard to come to a concrete conclusion as to what ACTUALLY happened. Example being a rowdy scout who doesn't like X adult for whatever reason; starts telling people that X adult touched him inappropriately at 3 in the morning when everyone else was sleeping while they were camping. It's pretty much one person's words versus another, which holds little to no credibility in court. There's no CCTV's in the fucking woods, and even if X adult isn't convicted, their reputation will be forever tarnished (Think Ray Lewis/OJ Simpson/Kobe).
Not to mention any openly gay scouts in the program will no doubt be bullied and harassed once adults have their back turned (Like I said before, roughly 3-5 scouts per adult, and scouts are usually on their own).
As I was saying before; pretty lose-lose for the Boy Scouts which is a shame for such a fine organization.