Like I said, Jason wants to include this for his own reasons and will probably do it at some point despite the polls never showing much interest in the feature.
The best work around right now is to just make a 2nd install of LB for kids and guests who you don't want to have access to your naughty games. The simplest way to do this is to make a copy of your LB setup, assuming your games and emulators are stored outside of your LB install folder and go through and remove the games. Another possible temporary solutions is to go through and mark the adult games as broken and hide broken games.
I know neither of these solutions are as good as a proper adult filter mode but I do believe Jason will implement it sooner rather than much later.