This is an example of the law treating a young adult as a child. A 17 year old is not a baby and should not be treated as one. Many of the laws in several English speaking countries relating to age based issues were changed without thinking them through last century.
As an example, until 1991, women in Australia could marry at the age of 16 (or even at 14 with parental consent). The only reason the age was raised to 18 was because it was seen as a symbol of inequality. Did anyone take into account that young ladies generally mature faster than their male peers? That was the whole reason for the age difference in the first place.
I'll agree that it was stupid to create a situation where the policeman's job and name would suffer as a result. But the very idea that 17 year olds need legal protection to stop them from doing what many of them want to do anyway is irrational. For thousands of years young adults have married and started families at ages that suddenly somehow became disrespectable in the 20th century
Can't the lawmakers see the problem with this?
I have cousins who were mothers at 16 and now one of them is an awesome mum with lots of little walking noise machines around her house. She's happy, she's strict but fun, and the children love her. Now I wouldn't encourage young people to race into these things, but some of them are going to do so anyway and their lives would be a lot better if we as a society supported them instead of condemning them.
At the same time, had this young lady been a year older, nobody would have cared. So why should the punishment for an image of a 17 year old who herself choose to take and send the pictures be the same as the punishment for an image of a six year old who did not choose to have her image taken in a certain way? Laws ought to recognise real differences between cases.