> This publisher is operated by a conservative think tank

Ok so I'm glad we're engaging the article on the surface.

> This article furnishes no evidence that being married forces poor people to be good parents

I'm not sure that was ever said. What they're arguing is about how societal institutions like marriage have largely declined and it's happening along with other large changes in society: lack of trust, friends, etc.

And clearly from what you've said, the legal distinctions of marriage are far less important than whether there's two adults in a family raising children.