"I don't think it matters where that Gif of Lila Perry was taken, or what Lila's "famous" for; if it were an 18 year old with female anatomy, would any of us think it was okay to be assessing her erect nipples or damp crotch to evidence..."
Are you actually serious? I mean really?
To the extent to which an 18-year-old female might have 'erect nipples' or a wet crotch, she is likely to be the recipient of unwanted male attention in consequence.
I mean the scenario where a female has a publicly visible wet crotch
is really only because she's menstruating, and for you to equate that with an erect penis is quite offensive. And protruding nipples are an OBJECT of male attention, they are not EVER a perpetrator of sexual assault in the way that an 18-year-old boy exposing his erect penis would be.
The sexually aggressive act of indecent exposure is about the deliberate exposure of a penis. It has bugger all to do with erect nipples or wet crotches!