What I have entitled the Pessimist Gap is the gap in reality-experiencing an 'unenlightened' person, let's say, and a Pessimist's experience. The Pessimist sees no reason to live such pointless lives where so little happiness is guaranteed, and where no one comes out alive, hence why there is no reason to breed. Hence when this very same Pessimist looks upon one who is not quite so pessimistic, they cannot see why exactly it is that the non-pessimist appears as if the horrible, desperate situation of life and the universe does not vex them in the slightest. It is the same for most non-pessimists out there, as far as appearances go. The simple solution is that things are not as they appear, and there is actually a gap between the realities that each player is perceiving.
This strangeness is explained by the fact that it appears perfectly obvious in the non-pessimist world that obviously we will be happier in the future, because we'll get that new bathroom suite we've always dreamed of! There is obviously a point to life, but we'll leave that for philosophers to figure out - common folk needn't worry themselves with such things. Death isn't final, or if it is, all the more reason to enjoy one's life and pass on the gift to others! The horrible situation we pessimists talk about is not at all horrible to anyone that is in 'Realist'-mode. Not even the absence of free will, which destines us to a multitude of suffering we neither wished for nor did our parents wish for, manages to knock people out of their trance. Don't think. Feel. That is the message of the Realists. As long as you feel happy, it's okay to have children. Don't question anything, so don't question the most basic premises of life to check if they are built on steady ground or not. Don't check whether the biggest decision of your life is the right one or not. Don't think - feel.
So are they brainwashed then? Does that not imply that the natural state of human beings is one of questioning reality? Well, that could be true, but we'd need a study done on existential thoughts in people first. I don't think genes would really allow that, but then, they don't control absolutely everything. It could be a universal fault impossible to get rid of that just comes with the territory of an advanced brain.
But if it is brainwashing, then in a lot of cases it is voluntary brainwashing, as a lot, A LOT of depressed people have these thoughts, and those who become cured basically still go on to have children, or to believe in (a) god(s), or to write happy self-help books about how life is great.