As simple and obvious as it sounds this is a profound topic.
NASCAR now has women driver (the hot Dannica Patrick), PGA features women golfers too (despite them having LPGA). I haven't seen a rule in FIFA that says women players are barred so if a capable one comes I am sure she will be allowed, but since there is a women world cup I might be wrong.
To me, unless a sporting event has men and women category, women are allowed. The category is not being sexist, it is similar to different weight division in boxing. Sure, many sports don't allow women and those can surely be labelled sexist if a woman is barred from participating in it. Unless there is a sports that involves your "tool" I don't see a reason why women shouldn't be let in.They will simply get out in the first round 

The argument about physical superiority might not hold true though it sounds logical. With that argument us asians, with some exceptions (which women also would have), should not compete with athletes from other continent who are a foot taller and hundred pounds bigger than us.