On the most simplistic level, religiosity can lead to irrationality, unless one is mentally ill to begin with and believes he is, say, Jesus, or that the voices in his head are direct orders from God or Satan. because it jacks free will and personal responsibility.
Although raised in the first ever protestant denomination of the Christian church (Henry the VIII's invention), I no longer practice nor believe, although it has been oh-so-tempting to give it over to God on those occasions when life seemed too hard to manage. But defaulting to God is like reaching for a Xanax. There ain't no Big Daddy in the sky. Ain't no dinosaurs in the Bible.
What if the Ten Commandments were some mortal person's attempt at crowd control in a time when people didn't have self-restraint? Ten bad things about covers it and still apply. In order to get people's attention, he'd have delivered them in a dramatic fashion and the results probably would have seemed magical, as people internalized the message and saw how much better every one behaved, especially once consequences for bad behavior were imposed. If you didn't get caught by the people who put themselves in charge, you would get punished in the afterlife, about which there is much fantasy in the absence of actual word form the other side. In other religions, you can blow up yourself with a bunch of other innocents and graduate not to Hell, but to a Bud Lite party.
Young, impressionable, and naïve people are good candidates for gangs and cults, and conservative or extreme sects, and even mainstream religions. These alternatives to reality and their relinquishing of personal responsibility (in favor of "God's Will") can become dangerous to the rest of us when people become insensibly certain their cause is righteous and that the hereafter is more important than the here-and-now.
Among my biggest fear lies in the growing disparity between the number of boy and girl babies born (or that are allowed to survive) in places where sons are saviors and girls are a burden. What do you think these single guys will do when they reach their teens? They are probably less desirable because they have no financial prospects to begin with, and have nothing to lose. They are likely to join radical groups that skillfully re-direct their frustration toward something else, like people who are different from themselves in heritage, nationality, or religion. What would almost any male who learns he will never have consensual sex (with either gender) do?