I was horrified by the murder of Dr. George Tiller in Kansas on May 31.

So when I heard there would be a vigil commemorating Tiller in front of the San Francisco City Hall, I attended.

Tiller was one of the few providers who performed late-term abortions, which are done for a variety of reasons, but often because of “fetal defects.”

It wasn’t easy for me to be there.

I’m a mother who has had an abortion.

I’ve worked as an abortion counselor, and I’ve been a longtime proponent of reproductive justice.

So I should have felt right at home at the vigil, but I did not.

Here’s the reason: At the vigil, one speaker after another talked about needing the right to have an abortion so as to avoid giving birth to a baby with a genetic anomaly. One speaker who had an abortion for this reason explained how the doctor who had performed it reassured her with pictures of the healthy babies women had given birth to after they’d had abortions for reasons such as hers.

I think of myself as healthy, I go to yoga classes and bike and eat lots of organic fruits and vegetables. My doctor, looking over the results of my annual blood work, saw my cholesterol numbers and said, “Go eat some Haagen-Dazs.” But sitting there in my wheelchair at the steps of the San Francisco City Hall, I knew that when people were talking about “healthy,” they were not talking about me.

At the vigil, mostly I heard about the “tragedy” of “fetal defects.” The unstated assumption was that disabilities are bad, and of course we should want to get rid of them. If that’s not possible, we should prevent the birth of someone with a disability.

These unstated assumptions concern me. We need to be wary of the dangers of talking about choice in a vacuum, of not acknowledging the social and economic forces that shape our individual “choices,” and the impact that those cumulative individual choices can, in turn, have.

The strongest support for abortion comes in cases of “fetal defect,” but I think that tells us less about support for abortion and more about society’s fear of disability.

Let’s face it: Disability is a part of life. People are born with disabilities, and they acquire them later in life.

You could become disabled while you are in a car, backpacking, diving into a swimming pool or, as happened to a friend of mine, sledding down a hill on a school cafeteria tray.

You could get an infection or develop an autoimmune disease.

In fact, disability probably will happen to you or a family member; it will almost certainly be a part of your life.

I urge my fellow supporters of abortion rights not to reinforce prejudices about disability.

We cannot allow ourselves to become a force for oppression of one group in the name of liberating another.

Anne Finger is a writer who lives in Oakland, Calif. Her next book, a short story collection, “Call Me Ahab,” will be published by the University of Nebraska Press in the fall. She can be reached at pmproj [at] progressive [dot] org.