If a person is a bigot already they will use their religion as one more excuse to oppress people. The problem is that this same religion will also encourage them to impose those beliefs on their children, raising them as bigots and making them think that God is on their side and that scripture supports this view. T hey would very likely impose these views on their children anyway, simply by raising them in a racist environment. Religion represents a huge financial and work burden on mankind. Imagine how that effort could be better spent.
Many theists believe in miracle healing.
Some theists have died because they have refused blood transfusions on religious grounds. Religious believers have been known to murder their children rather than allow their children to become atheists or marry someone of a different religion. Religious leaders have been known to justify murder on the grounds of blasphemy. There have been many religious wars. Even if we accept the argument that religion was not the true cause of those wars, it was still used as an effective justification for them.