Or, perhaps, invulnerable to abuse.

Religion is a big and complex topic. For starters, even defining the world religion is hard. So you have to start with a working definition and go from there.

One helpful way to understand religions (sorry, not enough time to define it), is that they typically start from an identification that life is unsatisfactory, and/or meaningless, and then identify some sort of solution, or salvation. Along the way they also try to answer fundamental questions of life like, who am I? Who are you? and What is this word?

For example, some Christians could be said to identify the suffering of life as being due to selfishness and disobedience to God, which results in suffering and ultimately, death. So the solution is having faith that Jesus fixed all that, resulting in an eternal life free of suffering.

Conversely, some Buddhists could be said to identify that eternal life is our problem, that is, we experience the samsara cycle of endless birth, life (of suffering, unsatisfactoriness, meaninglessness), death and rebirth. So salvation is in a sense achieved through escaping this eternal life through mediation and non attachment to your idea of the self - so you have to 'die' in a sense - so the complete opposite in some sense to Christianity! They start with the same problems but go off in completely different directions for solutions.

This is a very broad generalization and the main religions have enormous disagreements and divergent thinking amongst them. But I just try to give the jist of things.

And also, they are a great tool to oppress or liberate people depending on the personalities of adherents, especially the rulers (that German guy around the time of WW2 loved it, and cobbled together his own). This is why you can meet both really great and really awful people involved in all kinds of religion. Very powerful ideology. And if you're not careful, it's easy to hurt yourself and others. Beware!