I don't have an answer here, just a note that this question actually contains two questions, and it would be good to answer both of them together. It would also be a good example of using rationalist taboo.

A: What are the community norms for defining sexism?

B: What are the community norms for dealing with sexism (as defined above)?

Answering B without answering A can later easily lead to motivated discussions about sexism, where people would be saying: "I think that X is [not] an example of sexism" when what they really wanted to say would be: "I think that it is [not] appropriate to use the community norm B for X".