I am SO in favor of unisex toilets. There's a whole feminist argument about toilets/bathrooms etc (both public and private).
BUt - one serious point is, that the more public/open a place is, the safer it is. So unisex toilets actually make it LESS likely that a "perv" can spy on/abduct/assault children, whereas many people recoil at the idea because, you know, men would lurk there and do nasty things. The opposite is true.
However - toilets are often the safe haven of teenage girls who want to have a private discussion without boys listening in & taking over, so perhaps there's need to be somewhere for that - or we could educate teens to respect each other's privacy.