How do I judge? It's not that I don't, but I force myself to remember that in any group (and not in individuals, who can be evaluated separately, although in a related manner) there is a range. Just because SOME members of a religion (or political party, or social club...etc) engage in bad behaviors does not mean that the group overall is bad, or good, or whatever.
But some telltale signs: does the group impose strict hierarchy, giving benefits to a few while impoverishing the majority? Does the group highlight differences between people based on sex, gender, age, color, nationality, education and etc., with resultant differences in benefits they may receive? Are outsiders shunned, persecuted, treated as less-than-human?