A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.
I used to think this statement might have some element of truth, but that he was largely being flippant. I am now convinced that scarcely anyone likes having their beliefs challenged -- and this definitely includes scientists -- and scarcely anyone will fundamentally change their minds whether on an afterlife, political position, or whatever. They hold tenaciously to those beliefs no matter what. I now believe that presenting counter-arguments is largely futile. People don't want to hear, don't want to think. They'll seek out those people and views that confirm their existing beliefs.
I'm now convinced that what Planck said is mostly true.
18/05/19 Edited to add:
Rereading the above I think I might be conveying the impression that I'm bitter. This is not the case at all! I'm not talking specifically about my attempts to convince people; it's rather a general observation about the way people are. I've long been aware that peoples' minds are seldom changed, at least on the important issues. But I'm now convinced that attempting to change peoples minds, at least by intellectual argumentation, is pretty much of a forlorn endeavour. And I think that in itself is extremely interesting. I think we only change peoples' minds by appealing to their emotions -- trying to get others to empathize with your view, utilizing humour, and so on. And it almost certainly has to be face to face communication. There is so much more conveyed in body language.