Props for pulling the sources!
Though the other commenter saying “that sounds like it is made up” is definitely not presenting an opinion as fact, it is challenging that you presented your opinion as fact (in the uninformed person’s eyes) with no sources to back it up (in your original comment). But then you came with proof afterwards that it has indeed been studied and is a fact.
That does not mean that he was “stating his sexist stereotype as fact”.
If I said:
“Multiple studies have shown that the majority of people think the earth is flat”
with no sources.
Then anyone would be very reasonable to say “that sounds like you are making it up” (which in this case is true).
I didn’t realise it wasn’t the same person. The original comment I reacted to wrote this:
No shit it’s correlated more women want kids than men. Professor was a dipshit
Which has 50 upvotes still. It shows me that people accept this theory without the need for sources out of sexist stereotyping. No one responded with “you are making it up”. Instead it’s accepted as truth.
While demanding sources when I write the opposite.