Oh, and they only defend the worst of the worst.

Naw, more likely people only hear about the most dramatic examples. The every-day, my boss is picking on me stuff rarely gets much attention and is generally resolved quietly.  

Litteral thief, stealing, caught on camera, multiple times ? Well defend you tooth and nails. 'Til the management litterally had to get police involved for them to back down.

The severity of the accusation shouldn’t disqualify someone from their union defending them. Also, for a criminal matter, why didn’t they go the police to begin with?