I would absolutely get myself dragged into the HR office for this but tbh I would seriously consider talking to this coworker and saying something like:

"You know, I was thinking about what you said about how I shouldn't raise kids because I would raise them vegan and you're right about that. It wouldn't be fair to the kids.

By the way it made me realise that you shouldn't be raising kids because you are purposefully raising them Catholic, to the exclusion of all other religions, and that is unfair and unhealthy for your children.

What you really need to do is to take your kids to Sunday mass one weekend, then to an ashram the next weekend, then to a gurdwara and a mosque and a synagogue and a mashrik al adhar... oh, and don't forget to teach them all about Lutheranism too - it's really important that you offer your children the opportunity to understand all of the reasons why Martin Luther believed that the Catholic church was detestable and a perversion of the Christian faith.

Let your kids pick which religion they want to follow. That would be the right thing to do.

If I want dietary advice for raising children, I'll go to a pediatrician. If I want moral instruction for raising my children, I will go to people who practice what they preach.

And if you want to feel better about what diet I choose for my own children then maybe I'll speak some words of incantation over the vegan meals I prepare for them and I'll convince the kids that this magically transforms the dish into meat.

Anyway, I appreciate these little heart-to-heart moments we can share together about raising children and how comfortable you are with me that we can be open about this. Let me know if you want to do it more often."

I would get myself sacked for saying this kinda shit...

Don't do it.