The original BMW X6 challenged SUV orthodoxy back in 2008, and was crucified by critics as a result: Too heavy, too profligate, too impractical, said the industry ayatollahs—the same crowd that routinely fellates every portly $200,000 Bentley that comes down the pike.

Sure, by slicing and sloping the roof of the X5 on which it’s based, the X6 announced that style and performance were its primary mission, not ferrying brats to bassoon lessons. And that—the insistence that an SUV had as much right as any other car to ditch responsibility and just be fun—was the BMW’s unspoken crime, if critics had been honest with themselves.

Tellingly, the man on the street—and the woman, too—had no such issues. He got the X6 the second he laid eyes on it: It’s totally bad-ass, an artillery shell on wheels, strikingly proportioned, decisively masculine. And it’s still more practical than a sport sedan, with a touch of AWD ground clearance, fold-down rear seats and a decent cargo hold. The X6 proved an instant hit, with 200,000 sales and counting. Like other controversial BMW innovations, the X6 spawned imitators, including the comparatively awkward soon-to-be-released Mercedes GLE-Class.

For 2010, the X6M (and X5M) gained performance to match the superhero styling, and again managed to piss off traditionalists: Its twin-turbo V8 marked the first use of turbocharging by BMW’s storied M division, now adopted by the M3, M5 and M6, and also became first with AWD.

That brings us to today, at Monticello Motor Club. At this devilish road course near the Catskills, we’re rocketing the redesigned X6M down the long straightaway to the tune of 150 mph, lap after lap. It’s a ridiculous speed in a 5,000-pound SUV that would seem to have no business on a road course. Yet it does, in the hell-with-physics fashion that’s only gotten better in this second generation: Upped to 567 horsepower, the new 4.4-liter twin-turbo V8 catapults the BMW to 60 mph in a shocking four seconds flat, with a smooth eight-speed, paddle-shifted conventional automatic divvying gears better than the previous six speed. Torque jumps 10 percent to 553 pound-feet and peaks at just 2,200 rpm, the better to blow away unsuspecting two-seaters at stoplights.

The BMW X6M is totally bad-ass, an artillery shell on wheels.

The body stays flatter than a Marine recruit’s buzz cut, with less push from the front end. The ingenious torque-vectoring rear axle overdrives the outside rear wheel to help this beast scrabble out of turns in a way drivers can really feel. The rear-biased xDrive AWD system can send 100 percent of torque to either front or rear wheels. Launch control will both dazzle and discombobulate your bros. The stability system’s M Dynamic Mode even lets the X6M execute some stylish drifts, like a hippo on skates, before it reels everything back in.

Upping the previous 20-inch wheels to truly gigantic 21-inchers, with sticky Michelin Pilot Super Sport tires, makes room for brakes with 50 percent more surface area. Throw in six-piston calipers up front, and the BMW has the braking power that’s especially critical in this large-scale machine in which pilots could otherwise get in over their heads. The brakes start feeling a bit spongy after five brutal laps, yet a quick cool-down has them ready to rock again.

New electric steering doesn’t transmit much of the road surface, but it’s better weighted than the previous, overly leaden hydraulic unit. The interior is sweet, too, with body-cuddling sport seats, a thick-rimmed M steering wheel and an optional full-leather wrap in soft Merino hides. Even BMW’s stubby, smooth-headed console shift knob—it recalls a high-end sex toy from Berlin—seems to work more pleasurably than before. To shift gears, that is.

The X6M starts from $103,050, but with infrared Night Vision and a few other goodies, reached $115,150. That’s a lot of dough for this Bavarian creampuff. But it’s about $53,000 less than the base price of the 570-hp Porsche Cayenne Turbo S, the only SUV right now that can challenge the Bimmer’s performance.

The only tears flow at the pump: The X6M drank a gallon of premium unleaded every 12 miles, though a lighter touch might get you closer to 16.

Like the Porsche, the BMW is still no sports car, despite prodigious power and roadholding grip. Instead, it’s a freak athlete, a linebacker with a blazing 40-yard time that’s out to knock everyone’s dick in the dirt. Yet the sheer improbability of the X6M’s performance makes it a hoot to drive: 2.5 tons of big-bootied fun, in a BMW that knows how to shake it.

Follow Lawrence Ulrich on Twitter at @LawrenceUlrich