http://www.mass.gov/ocabr/docs/tenantsrights.pdf
http://www.mass.gov/ocabr/docs/landlordrights.pdf

As you can see these pamplets that Hud/Section 8 gives out the land lord is not responsible for settling disputes between tenets. they are responsible for working out disputes that cause the tenet a problem with living up to their contract (According to HUD/Section 8 this means if there is a problem with the unit that is causing the person to not be able to pay their rent, try to work out a payment plan if tenet has a financial problem come up that affects their paying the rent one month,... problems that are addressed in their contracted lease that would otherwise get the tenet evicted)