That statement is plenty stupid for a number of reasons but just one of which is, children don't become socialized by being in one room all day with 10 other children the same age who are also not socialized.
My poor children that I stayed home with when they were babies to pre-school. As adults I can see what you mean. My son is a Supervisor for a large oil company. I have one daughter in University. I have another daughter engaged. And, oh no! I'm now raising a babe and staying home with him. How are they possibly coping seeing as I messed them up keeping them home with me and not putting them in daycare?