I find religion less poisonous than spirituality. In the same fashion, I find forms of introspection incredibly damaging.
We are tools of evolution. We are here to produce, consume, and breed at the fundamental level. The beauty of life is that evolution endowed us with emotions in order to do this in such a manner that we can love producing, consuming and reproducing.
Our mind is a tool that senses and interprets reality. We use that information to act on our desire to accomplish our goals. I find that religion can often be harmful to these ends, but what I find vastly more harmful is spirituality and certain types of introspection. When our mind turns its powers upon itself it is a hall of mirrors. There are no answers when a sensor reads a sensor. This turns people erratic, highly emotional, and constantly looking for answers with only momentary glimpses of a perception of confidence in what they believe.
The people who turn to spirituality/introspection become lost in their minds. They disconnect themselves to reality. They become highly influenced by gurus and others who confirm their spiritual assumptions. They feel unsupported by people who don’t validate their premises, and they further seclude themselves in their narratives.
Religion doesn’t often have this effect. The narratives aren’t turning the mind against itself. The narratives are social, and turns the minds towards an external purpose of reality. While the narratives can be inaccurate or harmful, I believe someone can be happy while being religious vastly more than with spirituality.