Ideological commitments can lead us to deny what is obvious to any reasonable person. I find it hard to make sense of the claim that life is worse for the average person today than it was, say, one hundred years ago. That seems like gaslighting. But I suspect that very few progressives actually believe this.
The reason so many progressives love to hate Pinker and his fellow possibilists probably has more to do with human motivation and social change.
Progressives are always comparing the present to an ideal. Of course, some ideals are more attainable than others. It’s always useful to ask: What is our end game? What would it take for us to be satisfied? Some progressives have a clear sense of this. Others do not. In the latter case, dissatisfaction with the present is built into their modus operandi. For this group, to be a progressive is always to compare the present to an unrealized and often unrealizable standard, thereby providing a reason to keep on fighting the good fight.
https://areomagazine.com/2020/11/10/why-progressives-downplay-progress/
If you want people to act, you need them to care, and if you want them to care, you need to get them riled up. If you want to start a social movement, or bring about social reforms, you need to make people feel a sense of urgency. Moral outrage, not bare facts, stirs people to action. I cannot think of a single significant social reform that was not born of a deep sense of dissatisfaction with the status quo.
Thus, progressives reject the story of progress not because they reject the facts it entails, but because they see it as a threat to future progress—because they think that the only reason we have come this far is because we have resisted concentrating on our achievements. They don’t hate progress: they just hate talking about it.
If this is correct, we are left with a paradox: in order to achieve progress, you have to downplay (or even deny) its existence. This would explain why so many progressives have trouble listening to claims about how good things are, or how much better they are than they used to be. While they might be empirically accurate, such claims sap the energy we need to keep moving forward.