I have to agree with you. My personal feeling is, if the celebration progresses to the point where you're setting fire to the in-laws, you really shouldn't have opened that last jug of Manischewitz.
The wicker man ritual was described by Julius Caesar in Book Six of The Gallic War, in which he describes the customs of the Celts of Gaul. He writes: "The whole Gallic race is addicted to religious ritual; consequently those suffering from serious maladies or subject to the perils of battle sacrifice human victims. . . . Some weave huge figures of wicker and fill their limbs with humans, who are then burned to death when the figures are set afire. They suppose that the gods prefer this execution to be applied to thieves, robbers, and other malefactors taken in the act, but in default of such they resort to the execution of the innocent."
Caesar wasn't the type to retail wild stories. On the other hand he evidently hadn't witnessed a wicker man sacrifice himself, and as far as I can tell no other classical author mentions it. So it's hard to say how common this practice really was.
More recent takes on the wicker man have been only marginally less macabre. At the genteel end of the spectrum are the modern pagans who reenact wicker man burnings as a purgative ritual. No humans are actually burnt, aside from the occasional warlock singeing himself with his Zippo.
Far more interesting is the annual Burning Man Festival, a bizarre combination of participatory art event and beer blast held the week before Labor Day in the Nevada desert. No direct line can be drawn between the Gallic wicker man and the Burning Man Festival, which drew 15,000 this year. The festival, I'm told, began when one of the founders torched an effigy on a San Francisco beach in 1986 to purge himself of negative vibes after he broke up with his girlfriend. However, if we consider the salient features of the Gallic and U.S. events... flaming destruction of a giant wooden man, frightening pagan rituals, torching of the innocent (well, severe sunburn and dehydration of the innocent, anyway)... we see that they're closely related. Or more accurately, that they spring from the same font of pyromania that makes kids join the Boy Scouts. It's been described as a testosterone-driven affair in which any number of art, uh, thingies, many of them quite impressive in an unhinged sort of way, were assembled and then gleefully destroyed over the course of the week. The grand finale was the destruction of the 50-foot-tall Burning Man himself, which was accomplished with enough flame, explosives, and noise that I daresay even the guys in my old Italian neighborhood would have been impressed. For more, see http://www.burningman.com .
A similar event, although presumably lighter on the sex and drugs because it's sponsored by the Kiwanis, is held in Santa Fe, New Mexico, where a giant effigy called Zozobra is put to the torch as part of the annual fiesta, said to be the oldest civic celebration of its kind in North America. Again, no strict connection to the Gallic wicker man... just more proof that moths ain't the only critters drawn to flame.