San Francisco: Harassment/ Threats by Tenant

[Caitlin Nolan]

My partner and I currently reside in San Francisco. While I work full-time, he manages the building in which we live. It is owned by his father who lives permanently in Prague. 

We have one sub-tenant that has lived in our unit for ~7 years (because, rent control) and the atmosphere has gotten tense recently due to false claims of harassment he's submitted to the SF rental board (e.g. saying we tried to wrongfully evict him, or that my partner is unresponsive to his request). The truth of the matter (and what makes us most upset) is that he is blatantly lying and his accusations are completely unprovoked. I have personally lived in the unit for ~2 years and the only reason we can think he would begin doing this is because he feels threatened by our relationship (sub-tenant and my partner used to be good friends). Maybe the typical "friend-gets-into-a-serious-relationship, other-friend-feels-abandoned" scenario? It sounds petty, I know, but we have no idea why he is acting this way. As many of you may already be aware, it's very tough being a landlord/ master tenant in SF, so we are out of ideas or options in dealing with this.

With that said, my questions for the forum are: Has anyone been in a similar situation (in San Francisco)? What would be the best remediation in this case? Are we, the master-tenant/ landlord, able to file a harassment claim against him as well? Would that even accomplish anything? We would like to avoid any legal proceedings, but feel as though we really have no other choice at this point.