HUD has a helpful flyer about a landlord’s duty to ensure fair housing, including when the landlord is aware of fair housing violations caused by one tenant acting against another:
https://www.hud.gov/sites/dfiles/FHEO/images/owners-managers-508.pdf
CMHA encourages all tenants to report all suspected fair housing violations, including those caused by tenants.
In terms of policies, CMHA’s position has been that such behavior is a violation of the lease which the landlord should be enforcing.
For example, the lease should prohibit a tenant from breaching another tenant’s peaceful enjoyment of the neighborhood.