Well, if you grow up with abusive parents who were miserable and constantly depressed, you likely don't want kids to avoid going down the same route. But that sort of upbringing likely means you are miserable as well.

Happy people ought to have kids, since likely they will have happy kids. Unhappy kids ought to not have kids, since they will likely have unhappy kids, and would make themselves unhappier for it. How is this strange? Do you think that miserable people shouldn't be able to express their misery? do you think that hating those miserable people will help in any way?