Is anyone else dealing with an aging parent becoming a curmudgeon

I visited my father this weekend and left worried about him. First, my dad has a spotless record of being a well-respected and upstanding man. He's in his late 70's, but very sharp. He's married to a younger woman and is very active. But lately he seems to be overenjoying one of the key perks of old age: saying what is on his mind and not caring what people think.
When I arrived, I brought up my brother and dad immediately started telling me how disappointed he was with my brother's career change, saying 'I told him earlier that he's hyper-active and should find some ADHD medicine right away." I sort of laughed but noticed that this kind of talk had become a trend. Later that night we went on an errand and he flashed his brights at about 1 car out of every 3 or 4 that passed. When I told him that cars just have brighter lights he said, "You think I don't know that? I'm holding these a__holes accountable. The brights are out of control these days!"

On another trip, he asked some kid why he was leaving his grocery cart out in the middle of the parking lot. There's more, but is this kind of thing normal? TLDR/ Facebook: dad is kind of turning into a dick and I worry he may say something to the wrong person.