If you really want to improve your group's image, telling other groups to stop stereotyping won't work. The stereotype is based on the underlying distribution of fact. It is far more realistic to turn your complaining inward, and pressure the bad apples in your group to stop pulling down the average.
I'll admit that this sounds a bit harsh (maybe more than a bit). But before you write me off for my insensitivity, let me say that I follow my own advice. I'm a libertarian economist, and as a libertarian economist I face an array of negative stereotypes from mainstream economists, which in turn lead to statistical discrimination. Here are a few of the stereotypes:
There are roughly two ways I could try to defuse this problem:
1. Preach to mainstream economists: "Stop stereotyping us!" and pretend like there is no truth to these generalizations.
2. Preach to other libertarian economists: "Let's improve our image by improving ourselves."
I've been trying to do the latter for about a decade. For example, I wrote my essay "Why I Am Not an Austrian Economist" because I think that libertarian economists are disproportionately ideologues who don't understand market failure arguments. There's no use pretending it isn't so. (For another paper I've written against mistaken views common in libertarian circles, see here; see also my debate with Pete Boettke).
Telling mainstream economists "The stereotype is false because some libertarian economists don't fit it - look at Milton Friedman!" is scarcely better than naked denial. Obviously, every stereotype has exceptions; stereotypes are useful because they are better than nothing, not because they are infallible.
It's far more productive, then, for me to exhort other libertarian economists to not be ideologues and get a firm grip on market failure arguments. Fight the stereotype by making it less true, instead of pressuring others to ignore what's right in front of their faces.
Similarly, when libertarian economists make mathematical mistakes, I try to correct them. If it were just a random economist, I wouldn't bother. But when a libertarian economist maintains that utility functions are cardinal, he drags down our average math score.
Admittedly, there are limits to my strategy. Another stereotype of libertarian economists is that they oppose discrimination laws. It's true, but I wouldn't try to undermine the stereotype because I think it's the right position. Of course, I would like to undermine the stereotype that we don't have good arguments for this position by making good arguments, but that's a different matter.
So am I saying that discrimination against libertarian economists is basically just statistics, not disgust? That's going too far; as I've previously argued, non-profits such as universities are a lot more likely to let taste-based discrimination survive than for-profits. What I am saying is that libertarian economists should recognize that negative stereotypes about them are grounded in fact, and the way to fight those stereotypes is to change the facts.