No pursed lips, no, I assure you. I went to school with those girls, and they were neighbours. It was extremely sad for the girls. None of them reached their potential in school. All were sidetracked by promiscuity and had babies during their teen years. Their self esteem was non-existent, probably as a result of how their parents treated them ("Fuck off to bed before I break your leg" etc. They were locked out of the house from morning to dinner time during the summer so that their mother could make it spotless, and they often asked neighbours if they could come in to use their loo.) They were abrasive enough characters in school, especially as they got to about 12 or so, and inclined to be cliquey.
Maybe it was a more innocent time and the parents of the neighbourhood, mine included, possibly thought it was none of their business, but looking back, there was a lot amiss in that home and a lot of people of my mum's generation wished they had talked together about things they were noticing at the time.
I stand over my opinion that a 4 year old girl wouldn't be normally or naturally inclined to lick a boy's penis. Maybe look (and maybe laugh or poke fun) but not lick.. I don't think this comes in under the heading of 'playing doctor'.
I disagree with your assertion that sexual abuse is more likely to result in aggression than in acting out of a sexual nature. Further, I don't think you can separate sexual abuse from emotional disturbance -- where there is abuse there is most certainly a lot of emotional fallout. When a child acts out sexually in this way, then it behoves those with responsibility for the child, or those who are concerned for the child to find the reason for the behaviour, find out what is disturbing the child.
What is a sexual abuse 'ishoo' and why is there an element of 'ner ner' on your part here?