1. Asking someone to self-censor might seem like a good idea, but is insulting and/or degrading. Don't. Having been on the receiving end of this, from people with the best of intentions, I now regret also having told someone to do this.
2. Don't expect people to change if they say they won't. Kind of obvious in retrospect. Instead change the majority of people who are willing to change -- your own beliefs are only the norm in your own little ghetto, you do actually have to sell them to the community at large.
3. Don't do nothing about insults that are clearly causing distress in the hope that things will get better on their own (see point 2). This looks like implicit validation of the insult even if that's not the intention.
3. Tolerance policies don't eliminate discrimination, they just make it harder to see. Discrimination now occurs in the negative spaces, the topics quietly suppressed. It's harder to see, for example, the people who quietly left for ghettos where they feel safe. Policies forbidding "inappropriate" public speech have a natural affinity with taboos such as "the sin that cannot be named". Private speech remains offensive, but with such policies it can not be publicly discussed. Voldemort.
I'm not sure what the solution is for number 3. Clearly it's a big problem. Possibly organizations need to make an official statement of being anti-discrimination (eg rainbow on the web page). Expand and eventually invert the ghettos. This means taking a side, which requires a consensus within the organization and requires effort even if the right side is obvious. It also strays toward thought policing. There's a delicate line, and I'm not surprised that people with the best of intentions are getting it slightly off.
Lazy web: Surely someone has thought about this more deeply than I have. Keywords?