It's ok to have children without getting married now, isn't it?

The title of this post is what someone said to me today, as a pointed accusation that I am secretly intolerant.

I changed the subject and felt hurt that they wanted to do this, and now I feel guilty I didn't respond properly, so I'm going to try and make myself feel better by writing here what I should have said.

Presumably you think it's wrong to cheat on your wife? Why is it such a stretch then to want to avoid "pre-emptively" cheating on her?

Should I bring it up tomorrow?