To this day I refuse to believe that Sarek is a bad father.
Yes, he and Spock often argued. That tends to happen sometimes! Father and son argue. water is wet, film at 11!
And Sarek had what I consider to be a perfectly good reason for being angry with Spock: Sarek had to choose which one of his children would attend the Vulcan Expeditionary Group. He chose Spock, AND had to lie to Burnham and say she was rejected. Then Spock goes and joins Starfleet, rendering the whole thing futile. I can't say I blame Sarek for being a bit cheesed off.
Sarek is a
conflicted father. He is not a
bad father. Far as I'm concerned, he did the best he could. I mean, look at how he reacted when he thought Kirk had abandoned Spock on Genesis in ST III. That is clearly the reaction of a loving father.
How's THAT for controversial!