I believe there are some mental handicaps where support dogs can play a role...
For example, there are some people who have a disability where they cant really control their muscle reflexes and end up constantly hitting themselves during a fit...
So there are dogs trained to sense when these fits are about to happen and physically place their body really close to the owners body, preventing them from hitting themselves till they calm down...
But for those that claim they need an emotional support pet just because (insert stupid reason) is really bad and doing a dis-service to true service dogs and the owners that need them...