Who said that every religion had to be “good” any more than who said that every drinkable liquid had to not be poison?
How about this for a high-tech definition:
Our culture, for instance that contemplated by the founders of our nation, distinguishes between murderous cults and "groups and beliefs" that personally seek to promote, elevate and preserve the good in humans.
One can clearly see the result when there is confusion on this issue; history is quite helpful in this regard.
Have a nice weekend.