Those kind of bomb sniffing dogs and cadaver sniffing dogs are morally acceptable, to me, personally.

The drug sniffing dogs aren't, not necessarily because its cruel to the animals, but because they have been shown to not be 100 percent reliable, and are commonly used by the police to abuse peoples' rights, as a tool to hide racial profiling, etc.

On the other hand, the police dogs that are trained and employed to bite people are an example of the extreme cruelty of humans, both towards animals and each other.