I am in the same boat as you. While it is very normal for parents to be defensive, I found the comment a bit unnecessarily aggressive without an immenent threat (heck, we're on some comment section on the internet here, not a dome in hunger games battling for survival).

But then again, I have not had children of my own, so I can't relate to the need to defend my offspring.

And from friends I know that parenting is really hard with lots of sleepless nights. Perhaps the parent commenter just had a bad day.