Some of the criticism is about showing the child in the photo. Though some object to the photo being shown at all. In many of the pictures the child's face is blurred out.
The police department said the purpose of the photo release was to illustrate how the drug not only impacts the users but also those around them. Especially children.
Personally I think they did the right thing. And what they did is not uncommon in campaigns against substance abuse. We see pictures in newspapers and on various websites showing before and after photos of how drug use radically changes the appearance over a short period. The same technique is also used in anti-smoking campaigns.
I say show the ugly side of drug use any time there's a chance. It might just save a life.