You said it Roberto, "sincerity and tact are key".
I am fond of the expression: that it's not what you say, it's how you say it.
Yes your father was tough, but I mostly agree with his attitude, his tactless insensibilities you had to endure.., well not so much.
Ironically, when I was a kid my father, who was a fortuitous full blown NW1 the majority of his life (7+ decades)and habitually humbly comported, would often vocalize personal anxiety/concern about hair loss.
It would take some collective effort on our part to reassure him that his hair quality and coverage was pinnacle caliber.
Another peculiar part to this story
is that he had promised to me on a couple random occasions, that I would never go bald?!
Maybe the worst part for me is that I believed him.
So yes,although almost tonally polar opposite in style at least, I will say that both our dad's ignorance of the influential power they wielded and it's far reaching effects on each of their sons, served to compound their son's future challenges confronting hair loss.