When we did have a Legitimate repair (hot water tank leak) the lazy x!

By all means, if there are legitimate child welfare concerns call the Department of Child Services (or better yet, have your tenant call).  

@Sarah Jones has a legitimate concern about dealing with firearms.

How legitimate does the tenant's complaint need to be to get protection from retalaition?

If you rent to them, you will need to use their current legal names in the rental agreement and have proof of their names supported by at least two pieces of legitimate ID.

A lot of people try to use the LLC to shield their assets and that is the purpose, but generally for legitimate business purposes and not for the pure investment used only for cash flow - those have been pierced by courts and will probably always be open to that. 

I don't know any legitimate Property Management company that doesn't have the authority to handle emergencies without your approval.

If there are legitimate health concerns you MAY be able to evict for health and safety issues.

It sure sounds like you had several legitimate reasons to withhold portions of the security deposit but it will ultimately come down to weather you properly documented the renter's deficiencies and if you did a proper and timely security deposit accounting per The laws in Massachusettes.  

There are sometimes legitimate reasons for medical accounts.