The MetaBrainz Code of Conduct currently does not enumerate unacceptable behaviors. The only clause that touches on issues of discrimination is the very vague rule 4:
MetaBrainz projects have global communities. Be mindful and respectful of different languages, habits and cultures.
I would ask that the Code of Conduct be updated to include an explicit (although non-exhaustive) list of unacceptable behaviors (such as racism, sexism, homophobia, transphobia, etc.) alongside these general clauses. Naming such behaviors is beneficial because it removes potential for discriminatory behavior being excused by claiming that actions that aim to address discrimination are in fact discriminatory against the original perpetrators, and also because it signals more clearly the good intentions of the project to potential targets of such discrimination.