Let me say this again. Parents should not be talking to umpires, period. It is not their place, nor does it change anything.
Of course, if you also mean to say that I can approach parents and criticize their parenting, then it's okay.
I'll offer three points in the following order: bad analogy, a great example of a good ump controlling a game situation by addressing fans, and an example of the OP's described arrogance.
PART I: First, let me agree that there are about 10,000 ways for a parent-ump conversation to go poorly and about 1 way for it to go well -- which is why there are a zillion league and organizational rules to discourage it. But, the analogy is broken. In the vast majority of games I watch or coach in, there are only between 1-3 people anywhere on the field that get paid. The umps. Everyone else is either volunteering or paying the umps. So, when you start paying me to parent my kids, then, yes, I suppose you can criticize me. The moment an ump takes the first nickel, he signs up for criticism. A lot of that will be unfair. Some of it will be fair. Take it or leave it.
PART II: Junior Varsity game, NFHS rules. Swirling winds with occasional sideways rain. My son's team on defense. Bases loaded and batter hits tall pop fly near the pitcher's mound. 3B, SS, and P all sort of dance around and nobody catches the ball. All runners safely advance 1 base, no outs. Parents (esp the pitcher's dad) were pretty confused by the lack of IFF. Not yelling, but vocally questioning the lack of a call.
I assumed that the definition of "ordinary effort" had been effectively eliminated by the horrible weather, but most adults don't understand the interpretive nature of the IFF rule. The umpire actually took the half inning and specifically address the parents in a very civil and polite manner. He explained the interpretation required by the IFF rule and that, in his opinion, there was no such thing as pop fly that could be caught with ordinary effort on this day.
Now, the fans weren't rowdy or rude, so the umpire had an opportunity to have a civil discourse. I was glad he did it. It hopefully educated the fans and really established control over the situation. Maybe it wasn't advised, but it was well executed.
PART III: 14U baseball governed by NFHS rules, 2014. I'm coaching. Regular league game. We're on defense, pitcher has runners on the corners. You know what happens next. My RHP feints to 3rd, comes off the plate, spins around, nails the runner at 1st. Umpire calls balk.
I approach the umpire and ask for clarification. Umpire explains that the "third to first" move is now illegal and a balk. I explain that the OBR has made feinting/faking to 3B illegal, but NFHS (and NCAA) have not yet followed suit. We play NFHS rules and, from the pitcher position, it's legal to feint/fake to 3B (and 2B) ... just not 1B. I, of course, lost the argument.
Not worth protesting. But I did contact the local league office and the umpire committee about the issue.
Week later, championship game. Same umpire crew. In the pre-game, I wanted to confirm that he now knew that per NFHS rules that pitchers could still feint to 3B. Nope, that would be a balk. At that point, I stated we would be playing under protest unless we got the head of officiating on the phone. We did and clarified this rule. Bottom of 7, 1 run lead, 2 outs, runners on corners, opposing coach screaming bloody murder at his players to watch the "third to first" move, my pitcher executes a "3rd to 1st" move, nails the kid, game over. Boy am I glad to have clarified the rule.
But it shows how arrogant a lot of umps can be. Even when confronted by a coach who clearly knew a lot of nuances about OBR, Fed, NCAA, it did not prompt him to go home and look it up ... if only to confirm he was right. And, it demonstrated a broken system, as neither the league nor the umpiring association followed up and educated the umps. And, this isn't a unique situation. Lots of other arrogant umps inventing rules -- turning left after 1B automatically forfeits protection, dropped 3rd strike and batter turns his back to 1B before realizing the drop is an automatic out for having abandoned his opportunity to advance, and so on.
Umps should be protected and shielded from angry parents. But, they also bear a large burden to hone their craft and to be a student of the game/rules.
Like the OP, I'm fine with umps who get the rules wrong. But, I see the same umps over and over who keep enforcing the BS make-believe rules, even after being confronted by coaches. That gets frustrating, because it's clear that they're not studying the rules ... or even reading them. Parents don't either, but then, they don't get paid to read the rules ... umps do.
But, I partially blame the NFHS for this. I can quickly and easily download and read every major rule book from MLB (OBR), NCAA, LL, USSSA (modified OBR), and so on. NFHS is the only organization that doesn't want its players, coaches, or umps to know the rules ... by hiding and charging for this most basic information.