For example, if you are Mormon and own a business. You have two candidates and one is a Muslim and the other a Mormon. Bias comes into play when you hire the Mormon even though they may not be as qualified as the Muslim may be. However, there are many, many instances of this outside of employment disparity.
This also occurs in social spheres as well, like making friends or dating. This is a major battlefront for us, not just gays but everyone LGBT and out. It also applies to persons of color and the not-so-hidden part comes into play with persons of color. I've personally witnessed marginalization happen very openly against persons of color, particularly trans women.
So what can we do? Here is a short list:
1. Point it out when you see it. Name it for everyone involved to hear. It may or may not change the situation but it will certainly begin the process of cognition. Change is slow.
2. Speak up for people who you witness it happening to. Making this socially unacceptable is not hard. Simply point out that it is distasteful and you do not tolerate it. Stick to your guns.
3. Console the victim. Be a friend.
4. Check yourself, it can be easy to make snap judgments based on stereotypes. Constantly be asking yourself why your making decisions and if you need, ask for assistance. Being open about this will enable education to occur. You don't know what you don't know...so ask for help.