NEW YORK — I was on my way home on the Cairo Metro, lost in thought as I listened to music when I noticed a young Egyptian taunting a Sudanese girl. She reached out and tried to grab the girl's nose and laughed when the girl tried to brush her hand away.

The Sudanese girl looked to be Dinka, from southern Sudan and not the northern Sudanese who "look like us." She was obviously in distress.

I removed my headphones and asked the Egyptian woman "Why are you treating her like that?"

She exploded into a tornado of yelling, demanding to know why it was my business. I told her it was my business because as an Egyptian and as a Muslim who was riding the Metro, her behavior was wrong and I would not stay silent about it. I knew she was Muslim because she wore a scarf.

I told her that the way she was treating the Sudanese girl made the scarf on her head meaningless. Her mother asked me why I didn't cover my hair and I replied that I didn't want to be a hypocrite like her and her daughter.

As distressing as I found that young woman's behavior, I was even more distressed that the other women in the Metro car watched and said nothing. They made no attempt to defend the Sudanese girl nor to defend me when I confronted the Egyptian woman.

After the Egyptian woman got off at her station, I asked the other women why they didn't do anything. One woman said she stayed silent because the racist woman would've yelled at her. So what, I asked? If enough of the women had confronted her, she would have been outnumbered.

I apologized to the Sudanese girl for the Egyptian woman's behavior and she thanked me and told me "Egyptians are bad." I could only imagine other times she'd been abused publicly.

We are a racist people in Egypt and we are in deep denial about it. On my Facebook page, I blamed racism for my argument and an Egyptian man wrote to deny that we are racists and used as his proof a program on Egyptian Radio featuring Sudanese songs and poetry!

Our silence over racism not only destroys the warmth and hospitality we are proud of as Egyptians, it has deadly consequences.

What else but racism on Dec. 30, 2005, allowed hundreds of riot policemen to storm through a makeshift camp in central Cairo to clear it of 2,500 Sudanese refugees, trampling or beating to death 28 people, among them women and children?

What else but racism lies behind the bloody statistics at the Egyptian border with Israel where, since 2007, Egyptian guards have killed at least 33 migrants, many from Sudan's Darfur region, including a pregnant woman and a 7-year-old girl?

The racism I saw on the Cairo Metro has an echo in the Arab world at large, where the suffering in Darfur goes ignored because its victims are black and because those who are creating the misery in Darfur are not Americans or Israelis and we only pay attention when America and Israel behave badly.

We love to cry "Islamophobia" when we talk about the way Muslim minorities are treated in the West and yet we never stop to consider how we treat minorities and the most vulnerable among us.

The U.S. television network ABC recently staged a scenario in which an actor worked in a bakery in Texas and refused to serve an actress dressed as a Muslim woman in a headscarf. The scene was an experiment to see if other customers would help the Muslim woman.

Thirteen customers defended her by yelling at the clerk, asking for the manager or walking out in disgust. Six customers supported the bigoted clerk and 22 looked away and did absolutely nothing.

I wonder now which Egyptian television channel would dare to stage such an experiment? And which Arab television channel would dare to stage a program that so boldly confronts us with the question "what would you do?"

For those of us who move between different worlds - where one day we are a majority as I am as a Sunni Muslim in Egypt and another we are a minority as I am as a Muslim in America - it is clear that to defend the rights of a Sudanese girl on the Cairo Metro means to defend my right on the New York Subway.

We live in a world that is connected in unprecedented ways. And that connection now extends to rights. If we want our rights to be respected we must do the right thing, everywhere.

Mona Eltahawy is a columnist for Egypt's Al Masry Al Youm and Qatar's Al Arab. She is based in New York.