Why are we gatekeeping football? or any other sport or activity? Women's flag football is great for lots of reasons. More interest in the sport from a more diverse group of people, even out the numbers for Title IX so we don't have to worry about cutting other sports and so on. The biggest drawback is funding, of course, but I think flag football will lose less money than a lot of other sports. I hope we get girls wrestling too, because my 6 year daughter old loves it and all-girls would be a better environment for it.
Also, if a dude wants to play volleyball, great. As long as he is competing against other dudes. I think football is the greatest sport known to man, but there are a lot of kids who have all kinds of interests. Giving kids somewhere to find themselves in a constructive environment is by far the biggest goal and we should be making available every opportunity we can.