THIS is what you're choosing to be mad about? Out of everything going on in the world?
The truth is most people choose a name based on the biological sex of their baby. And the vast majority of people identify with the sex they were assigned at birth. Those who don't are a small minority, and if the baby happens to be a part of that minority, they could change their name if they so choose. The choosing of a name for them at birth does not have to revolve around that possibility.
This person made a simple and common error. There's no need to be difficult or to call them ignorant. Names based on biological sex are the standard, this person is not ignorant for going along with a cultural standard.
Also, you really need to practice what you preach, because the person who made that post never stated that they used she/her pronouns, and yet that is how you refer to them? Maybe you should stop judging people and focus on yourself :)