One of my relatives worked selflessly promoting fundamentalist Christianity all over the world. As a result of her dedication, she avoided getting the treatment that could have cured her brain cancer, and died way too young.
Fundamentalist christianity opposes birth control, abortion, and modern science, three things which continue to be essential in bringing humanity into harmony with the planet on which we depend. In promoting fundamentalist religion, my relative may have done more harm than good in the largest view.
I believe there is a lesson here, and it is not the lesson promoted by Randian Objectivists and their many predecessors, who claim that charity is futile.
The lesson is: it is essential to choose the correct side. The same is true in charity and trade and art and love, in all the ways we build humanity.
I pity the early slain Jesus, elevated to an object of pointless and obsessional devotion, and who could often see far more clearly than most of his time.
How then, shall we know which is which? Well, Jesus himself is alleged to have responded to this question: by their works.
But that answer is now quite inadequate, in part due to religions such as Christianity itself. We need a further developed answer now.
The answer seems to me now: that which promotes the greater harmony and solidarity in all its aspects. One of the more important aspects is living in harmony with our world and the other species within it. That cannot be done with a continually expanding human population.
Not choosing sides is choosing the wrong side, and has been the path of least resistance into futility for modern liberals (social democrats actually) in the USA.
There can be no final answer, while life continues. That is why fundamentalism is wrong.