Mother Teresa. Charities. Missionaries. Do Unto Others.
Religion or, rather, religious individuals, are touted as having done good in the name of their religion. Religious dogma encourages people to do good. Even if the fundamental beliefs in a God are wrong, shouldn't we still keep religion for this purpose?
Now, this isn't an argument as to whether or not the premise here - Religion yields a net good on society - is true, but whether its matters in terms of combating and eliminating it.
Superficially, from a purely utilitarian perspective, one may argue that, regardless as to the existence of a God, if belief in God results in a net societal benefit, then we should encourage it.
I disagree. A belief in Santa Clause may result in a net societal benefit, yet we have no qualms about allowing that belief to wither in children as they get older. Likewise we should have no qualms about doing the same thing to religious beliefs.