Make money doing the work you believe in
Poor people won’t stop having kids. It doesn’t matter if rich people tell them they shouldn’t, other poor people tell them they shouldn’t or other people who were previously poor but are now rich tell them they shouldn’t.
Any attempt to dictate what they should do is just a thought experiment; where we examine current conditions, aggregate what can be changed and hypothesise a solution.
But these “solutions” we imagine don’t do anything except reveal the boundaries of own imagination.
Rather than making the moral argument for poor people having/not having kids—something that no amount of finger-wagging on the internet will ever control—ask yourself why it is more ideal to imagine a hypothetical that controls poor people’s actions than it is to imagine a different societal attitude to the protection of children?
Why are we more comfortable imagining poor people will roll over to eugenics-like demands than we are imagining governments will roll over to providing a fairer society with more efficient social safety nets for people in poverty?
Why does the solution focus on pressuring those already at the over-policed bottom and not the unaccountable top?

