The pitfall of uncritically accepting a moral code learned from one’s culture, such as that offered by religion, is that it may include elements that are truly harmful to others. An individual raised in the environment of Nazi Germany would have the same deep commitment to that moral code as anyone indoctrinated into any external moral code. In the pre-Civil War South, ministers used the Bible to justify the enslavement of other human beings. The Bible and the Koran are currently being used to justify racism and homophobia. The results? Torture, murder, and suicide.
The highest level of moral development requires a critical examination of values using universal litmuses like harm done, fairness, and empathy. Without rational, compassionate evaluation of every aspect of one’s moral code the potential for harm is great. Religion is a barrier to advanced moral development.
Religion inhibits intellectual development. The touchstone for intellectual growth is changing positions when disputing evidence for a pre-existing belief outweighs supporting evidence for said belief. Most of the dominant religions require accepting the legitimacy of their doctrines not on evidence, but on faith. Faith is often considered an admirable quality. I do not understand why. Faith and gullibility seem to be two sides of the same coin. Webster's defines faith as, "(a)firm belief in something for which there is no proof." Gullible means, "easily persuaded to believe something." So, aren't faith and gullibility inseparable? In other words, wouldn't it require gullibility to firmly believe something without proof?
Believing without evidence is a slippery slope. If I choose to accept one supernatural manifestation on faith, am I not then susceptible to believing any absurdity? Talking snakes, invisible deities, angels, pixies, leprechauns, and unicorns are all supported by faith and disputed by reason. How does one justify belief in a god, but not in a pixie, or belief in some other god? Disregarding evidence in favor of faith-based beliefs perpetuates ignorance. Religion is a barrier to advanced intellectual development.
Religion obstructs social development. In a modern global community, appreciation for the benefits of cultural diversity is paramount. Of the six Americans who won Nobel Prizes for Science in 2016, all were immigrants. By nature, religions are exclusionary. They create an "us and them" mentality wherein the "us" are good and the "them," not as good. This kind of social identity has been at the root of every war since the dawn of time.
Prepackaged, religious beliefs rob people of the opportunity to create personal meaning and to truly define a unique understanding of self separate from cultural definitions. The number one regret of terminally ill patients is that they conformed to the values of others rather than living lives true to themselves. Religion is an impediment to social development.
Religion is a barrier to emotional development. Emotional maturity results from coming to terms with difficult, often frightening, realities. Failure to take responsibility for one's actions is one aspect of emotional immaturity. Children tend to blame others or make excuses for mistakes. Mature adults take responsibility, attempt to make reparations, and try to learn from mistakes. While Christianity holds the individual accountable to a degree, it also provides an easy loophole. Per Christian doctrine, serial killer Jeffrey Dahmer was absolved of responsibility for his actions before his death because he sincerely asked God's forgiveness.
Another element of Christianity inconsistent with taking responsibility is the concept of Satan. Satan is ultimately responsible for all evil in the world and God is ultimately responsible for all good.
By encouraging belief in a fantasy afterlife, religion inhibits adults from maturely coming to terms with mortality. Developing the emotional maturity to deal with the realities of death, unanswered questions, and all of the other uncertainties of human life without resorting to magic and superstition requires courage and unyielding integrity. One must be committed to all truths regardless of how scary or difficult. Religion impedes emotional development.