I'm sure this will sound sexist as well, but the chivalrous guys far outnumber the jerks. If someone crosses the line, by all means call the cops but also consider making an immediate and loud protest, and you might get help from an ad hoc group of temporary big (or little) brothers. A black eye and split lip might be the quickest way to teach some of these guys the right way to act.
If this is the case, why do these incidents keep happening?
I guess it comes back to the cliched "All that is necessary for the triumph of evil is that good [people] do nothing".
And having a stated policy in place is a pro-active way to demonstrate "Hey, in case you were wondering, this kind of behaviour's not okay and this is how we'll deal with it".