This is just the latest pop-culture manifestation of a long-term problem, which is the enduring, historically quite justified mistrust of the African-American poor and working-class of the police.

People in the ghetto don't love criminals. Often there is quite a bit of fear involved. But they are from the neighborhood. Snitching means snitching on one's neighbor, or someone related to a neighbor or friend. It's not like you are giving up a "criminal" --- you're giving up someone you know. Especially for nonviolent crimes, or crimes related to the drug trade, there's not much of a personal incentive to give up anyone.

Of course there wouldn't be a "stop snitching" phenomenon if there weren't a lot of snitches out there, the vast majority of whom cannot be confused with your average citizen. The most common snitches are, of course, those swept up for relatively minor drug offenses who try to trade out of their sentences to go up the chain.

And there is of course the natural human response to defy authority and maintain group loyalty. Police officers are notably reticent to snitch on their corrupt and/or brutal colleagues, of course, and so are soldiers. The basic impulse shouldn't be alien to anyone here.