To some extent a State is a gang, but at a larger and more sophisticated scale. So is any sufficiently large company. The 'criminal' aspect is always a relative measure.
One should generally prefer criminal gangs elected according to social contract, since they are basically "our* criminal gang.
As for moral relativism - not so much. There's enough consensus for judiciaries and criminologists to define objective criminal behaviours. I think you mean that we exercise more or less tolerance of the criminal behaviour of certain groups.