Well they can be tough. You have to, HAVE TO,
HAVE TO train them. They're not the type of dog that if you don't train them well with people and other animals that they'll do well. If not socialized they can become aggressive dogs. They're loyalty there is probably part of the problem, they're very protective. They are not stubborn like huskies though. Shepards are eager to please. But again, if not trained well they will become a problem dog.
And actually, German Shepards have been started to be phased out of the police force because of bad breeding. They aren't as agile anymore. Their backs have been made shorter as well as their legs over time. And they can suffer from hip dysplasia. The breed back then was a lot leaner and had longer legs.

A similar breed has been started to be used now.
even the police in the German state of North Rhine-Westphalia, who had relied on the dogs for years, recently announced they were replacing them with Belgian Malinois, because the less-popular Malinois were hardier and more reliable.
Source
Note their longer legs and less stocky and more agile appearance.