In particular with regards to gender roles.
So, time was women were for making babies and raising said babies. Men were for protecting and providing for the women. That was the roles society prescribed and there wasn't a lot of deviation from it. You did see outliers that didn't conform, but by and large that's how things were basically due to necessity. You notice many animals follow a similar structure. It is what is needed for the survival of the species.
Well that all changed, of course. We now have the problem of too many humans, not too few. Also many of the household tasks that used to take a ton of time are now automated (try washing clothes by hand, it is a full time job almost). So society changed. Women didn't need to place their worth in their offspring anymore. They could choose to be what the wanted, do what they wanted, and still be valuable. It wasn't about popping out babies.
Well, this is the other side of that: Men's value now no longer needs to be in providing for a family. They can have a family, or not, they work, they can stay at home, etc, etc. For some men, that means staying single.
However, some people, like this dude, have a problem with that. They think that men should be required to be providers to be considered "real men", should be required to fill a particular role in society.