There are many problems caused by religion, but let's consider one
that is very directly related. Let's consider the problem of how
there is something inherent in many religions which cause their
followers to want to proselytize by whatever means they have at
their disposal. They might, for example, try to get their prayers
into the schools. Or they might try to get their religion taught
in science classes. Can you see how people who do not want their
children brainwashed, or people who would like their children
brainwashed with a different set of Truths, might be justifiably
upset at this attempt to indoctrinate their children? Can you see
how the resulting friction naturally leads to a destructive
divisiveness and hatred amongst people?

You might also consider the problem of why almost every damn innovation
that has the potential to make life better for people is fought tooth
and nail by the people who stand to gain most from it (i.e. ignorant
folks like theists), and why those courageous enough to fight the
idiots are vilified, persecuted, and jailed, or worse. For example,
Margaret Sanger suffered this fate for promoting birth control. Does
it really make sense that it seems to be the rule in our society to
persecute those who use their brains to improve the human condition,
and reserve our praise for those who are content to live their lives
in stultifying conformity? I think not. I think our civilization
was built by the labours of those heretics, which for the large part
have been atheists. I think that the deluded idiots who persecute
them are much worse than useless.