On the one hand, it's sensible advice they are giving out, to an extent - after all, I ought to be able to go out and leave my house unlocked, as people ought not to steal other people's things; but I can't, so I guard against burglary as best I can - but when there appears to be no similar advice to men to, y'know, not violate women, it seems a bit one-sided to say the least.
Unfortunately, though, from what German posters are saying, Karneval is exactly the sort of thing these sleazemonkeys love: lots of close, physical contact because of the size of crowds = unprecedented opportunities to grab women's genitalia. I don't really know, though, how you would police an event like that: I suppose a really, really enormous police presence on the streets? It's not like policing for counter-terror, because the processes are different: any police people out here that could explain for us?