When is it okay to use the phrase "and that's why you don't have kids"? The answer is NEVER. Never should you ever utter those words to someone. I guarantee you that if you say it to a person/couple dealing with IF, it will scar them deeply.
This weekend we had some friends over for a BBQ. While we were playing a card game I heard these exact words said to my husband across the table. The person who said them was probably a little intoxicated but I was not and I heard everything. And although he shares a bromance with my husband where they don't commiserate over our IF struggles, he is well aware of them. I didn't want to start anything so I stayed quiet. Later that night as we were going to bed I asked Babe what he thought. He said drunk or not, he would probably have said it anyway.
This relationship is one I'm already struggling with and now I seriously would rather set it aside. I don't need that kind of negativity in my life. Aside from the douchey things he said all night long to myself and our other guests, this was by far the thing that stuck with me most.