The “soccer mom goes berzerk” mentality, where parents overtake their children in their enthusiasm for youth sports, is rife with comic possibilities. Just last week, “South Park” had Stan’s dad getting drunk at the Little League games and fighting with dads from the opposing teams — all while the children themselves tried to lose, because they hate baseball.

The makers of “Down and Derby” will not be happy that I invoked the vile name of “South Park” in a review of their sunny, squeaky-clean comedy, but them’s the facts: “South Park” addressed the issue cleverly, while “Down and Derby” is imbecilic, unreasonable and wretchedly unfunny. It begins unpromisingly but with salvageable ideas; however, as early as the 30-minute mark, it has squandered its remaining opportunities and given itself over to full-blown irritation.

The subject is not Little League or soccer but the pinewood derby, the annual Cub Scout tradition where the boys make small cars out of blocks of wood to race down a short track. As with all sports, the real-life joke is that the dads are often more competitive about it than the boys are, sometimes offering more than merely “supervision” in the design and creation of the cars.

And that, you will agree, is a perfectly fine premise for a family comedy. But “Down and Derby,” written and directed by straight-to-video family-flick veteran Eric Hendershot, is flawed on such a fundamental level that it cannot possibly overcome it.

You see, on this suburban street where dwell four families, each with a Cub Scout, the fathers are insane. The central one is Phil (Greg Germann), who has always resented being No. 2 in everything to Ace (Marc Raymond) across the street. But Blaine (Ross Brockley) and Big Jimmy (Perry Anzilotti) are resentful, too, and all four men don’t just gradually take over control of the pinewood derby from their sons. No, they actively and intentionally push the boys out of the process altogether, giving them cash to go to the movies (or whatever) while they stay home to work on the cars.

As if that were not enough, each of the men does it in secret, too, hiding his involvement from the other guys so his strategies and tricks will not be discovered.

The problem here, not to put too fine a point on it, is that this is stupid. The film is 5,580 seconds long, and not one of those seconds is believable. Yes, fathers may become over-zealous in their desire to help their kids (and by extension themselves) win a contest. But notice I said they BECOME that way. In the movie, the dads don’t “become” anything. Everything they are — childish, buffoonish, irrational and moronic — they are when they start out. Rather than getting worked up into a frenzy, they begin in one, scheming to eliminate their sons from the game as soon as the derby is announced. Most fathers’ over-reaching behavior in situations like this would be considered a “crime of passion,” occurring in the heat of the moment. But these dads’ sins are premeditated.

Phil is the focus, but we’re led to understand he represents the general behavior of the other three, too. When his son Brady (Adam Hicks) shows him his proposed design for the car, Phil openly mocks it and walks away from the table, declaring that if Brady wants to lose, he can do it without his help. And this bastard is our main character!

Later he sets up a track and all his woodworking tools — so he can make many different cars and do test races — in his bedroom. His wife, Kim (Lauren Holly, overacting every time there is a camera trained on her), is displeased but for some reason puts up with it, acting as though this is merely an eccentricity, rather than the full-blown psychotic behavior it is. She and the other wives eventually leave their husbands altogether and take the kids with them. I’m not sure which is less believable: that a father would become so obsessed with the pinewood derby that it would make his wife walk out on him, or that his wife walking out on him wouldn’t make him snap out of it.

Oh, I should mention that while he’s working 24 hours a day on the pinewood derby, Phil is neglecting his advertising job, where he’s supposed to be heading the all-important Yakamoto campaign. When the clients show up at his house and want to see what he’s got for them, do you suppose he makes up something off the top of his head, and do you suppose it has to do with pinewood derby cars, and do you suppose the clients think it’s brilliant?! Well, DO YOU?!?!!

Phil’s single-minded devotion to the pinewood derby makes him forget his boss’ name, or even that he HAS a boss. Later he and his friends break into Ace’s house to see his top-secret car design, and Phil winds up hiding under Ace’s bed for several HOURS. That is not the behavior of a man who is simply caught up in the excitement of something. That is the behavior of a man who is autistic. Is Phil autistic?

I don’t think skilled comic actors could have saved this lazy, pathetic script anyway, but we’ll never know, because these are not skilled comic actors. They are not comic, their skills are questionable, and I wouldn’t put money on their being actors, either. But I do sympathize with them. They are probably decent folks who were simply caught up in the fervor of making a movie, unable to discern until it was too late that what they were involved in was an abomination of biblical proportions.

F (1 hr., 33 min.; PG, a little mild innuendo.)