They have probably been trained to be vicious killers and are not safe for a family environment.
A police dog may be trained to bring down a fleeing criminal or demonstrator without killing him. But you can't take that chance with an enemy armed with a kalashnikov. They are probably trained to go for the throat.
They are trained to sniff and attack but they have been offered homes by experienced handlers who know what they are doing. All dogs are dangerous in the wrong circumstances and it usually turns out to be the stupid owners to blame because they couldn't care less, are ignorant, or are oblivious to the dangers some dogs pose.