You know, I'm not sure. I've seen the * used with transgender.
I've seen the * used with Trans as well and from what I was told it meant was that "trans*" is somehow more inclusive than "trans" and think the author of that piece was trying to do the same. I don't understand the whole * thing either, and a side of me rolls my eyes at it as nothing but people just trying to do things differently, but I don't think that detracts from the piece. The piece addresses the issue of why the billboard is racist perfectly by pointing out that in making children of color the victims, pro-life society will demonize women of color. It also does a good job of addressing underlying causes which create that trend.
I think it threw in the last two at the end as other sorts of societal and economic discrimination in our society (it came from a pro-choice* feminist author to the best of my research). While the latter two will rarely cause abortions, they are equally wrong.
*EDIT: D'oh. I meant pro-choice and had a brain slip and typed pro-life (probably because the author's name or my having a derp moment). Gyeonghwa's right and thanks for the correction.