Your dad's depression was not caused by the testosterone or by the urologist. Even if you feel the urologist did something improper by giving your dad the shots he was taking, being mad at the urologist is displaced anger at the situation, and is not going to improve the medical situation for your father, which is the primary issue. Your dad may have told himself he was doing it for his mood (even if you suspect otherwise) but obviously it hasn't solved this problem, and the issue now is to get him out of the hole he is in emotionally if he can get out of it. To move his care forward, he needs proper workups under a primary-care doc (which sounds like it is happening) and should go with what the primary-care guy recommends or prescribes. He should certainly be considering antidepressants or anti-anxiety meds, they will do much more for him than testosterone.
Once you get your dad out of the trough he is in, if you are still angry at the urologist you could file a board complaint, saying you feel the testosterone shots were excessive or unnecessary. But again, unless you can show they harmed your dad (you can't) and unless your dad was not in his right mind and you can prove the doctor knew it, the urologist's defense will be that the shots were at your dad's request. Unless what a patient requests is medically dangerous or simply blatantly unnecessary, usually it's OK to give a patient what he wants, especially if he is unhappy and feels it will make him happier. (And regarding everyone's judgement that these shots were blatantly or obviously a waste on such an old man, who is to say that a guy in his 70s or 80s does not have the right to request testosterone, on the chance he'll feel better? They might have indeed made him feel emotionally better.) Unless you can show that the doctor did something medically dangerous, such as not checking for prostate or heart issues, he (the doc) was probably within his rights to do what his patient requested.