I guess for me its the cases of misuse that are of particular importance.
Any form of governance is about as good as any other. Nothing demands that a Monarchy, a Democracy, Oligarchy, or any other should be better or worse the the other. We have stupendous examples of democracies select piss poor leaders, just as there have been bad Popes, Monarchs, etc.
Its that system's resistance to corruption that really sets one apart from the other. To me though, a religious order is the most highly susceptible to corruption, as it relies on small groups of people with absolute authority, and I have so little faith in people. The old saying power corrupts, absolute power corrupts absolutely, seems to be particularly poignant in this case.
I speak of governance, because major religions indirectly govern more people than any particular single country or government. This makes them extraordinary dangerous to the existence of humanity at large, again imo, regardless of how well - or unwell - they make the communities they are in. Its not the little things, the orphanages and the charitable donations, that worry me.
I would think, absent origin stories of our divine right over all things, a more peaceful humanity would develop. Burying good will, kindness, morality, inside of old doctrines that also carry within them a deep penchant for violence seems like a bad idea to me. Modern major religions seem largely as a means of mass control - through beliefs, they control thoughts, and therefore actions. Its easy to wind people up when religious lines start getting drawn, and nothing could be more terrifying, in my mind, than a call to arms by a major religious power.