I used to wonder what it would take to spur a mass uprising among black college-age women about the way they're depicted on cable outlets like BET and MTV.

Would derogatory terms bandied about like the filthy stuttering of illiterate school boys do the trick? Nope. What about a constant stream of video images reinforcing the dubious connection between black femininity, crude materialism and unhinged sexuality? Nope, that's just par for the course.

As it turns out, it would take a particularly disrespectful move with a credit card to finally generate outrage against a popular rapper unprecedented in rap music's 30-year history.

Marketing a sugar energy swill called "Pimp Juice" to gullible young people in ersatz malt liquor cans didn't get Nelly picketed. It's easy to see why the St. Louis native believed he was untouchable after getting away with that one. After all, people have lost jobs after uttering innocuous words like "niggardly" in the wrong context. But given what most rappers are getting away with these days, cultural affront isn't what it used to be.

Then along came "Tip Drill," Nelly's homage to ugly women who have great bodies but nothing else to offer the men who exploit them. Nelly's video ups the usual cringe factor a few degrees by introducing a credit card swipe through the buttocks of a thong-wearing woman, leaving little doubt about the object of his contempt.

The gesture, written to show how clever rappers from Missouri can be when forced to come up with ever more creative ways of demeaning black women for fun and profit, seems to have provided a moral tipping point for the students at an African-American women's college that was once a hotbed of social activism.

Spelman College students were so outraged by Nelly's video that they decided it was time to protest such a crude assault on their collective dignity.

I don't know why it took so many intelligent young women so long to get mad about the wholesale disrespect of their womanhood, but thank goodness they finally did. Waiting for the NAACP or BET to take the lead in criticizing millionaire exploiters of black women is like waiting for the government to apologize for slavery. It's not going to happen.

In late March, campus groups at Spelman sponsored discussions about the place of rap lyrics and videos in black popular culture. The students asked questions about the role of "unindicted co-conspirators," like the women who appear in the most demeaning videos imaginable for money.

Meanwhile, an April 2 charity benefit for Nelly's 4 Sho 4 Kids Foundation was scheduled for a performance at Spelman. The students decided that it would be the perfect time to confront the rapper with their concerns about his negative portrayal of black women.

Nelly may be a misogynist, but when it comes to his cancer-stricken sister, he has a heart as big as any in show business. After she was diagnosed with leukemia last year, Nelly formed the 4 Sho 4 Kids Foundation to educate fans about the need for bone marrow and stem-cell donors in minority communities.

Unfortunately, he has never striven for a similar loftiness in his public performances. Even while "pimpin' " for a good cause, Nelly continues to insult black women. When he learned that the girls of Spelman planned to picket his April 2 show, he canceled it. The rapper's management blamed the students for being unable to distinguish between an outrageous stage act and real life.

Well, shame on these women for standing up for their human rights. It's too bad leukemia research has taken a back seat to another skirmish in the culture wars, but what the Spelman students gained from opposing Nelly is another way of confronting an equally virulent disease.

Nelly is by no means the worst entertainer out there when it comes to actively disrespecting women. In many ways he's merely typical. Like most of his colleagues, Nelly assumes there will never be a price to pay for his cavalier assault on the female image. Fortunately, the women of Spelman have taught him just how outdated that assumption has become.