I do agree to a point but my point is, who is getting offended at this? I may well be wrong but I've only heard a couple of members of the public and a health care worker getting offended.
Edit: To add, these costumes are clearly exaggerated, cartoon like characters more akin to something from a film rather than a depiction of someone with mental health problems.
I find it offensive. There's a history of mental illness on my fathers side of the family. Two of my relatives have been hospitalised and my cousin ended up committing suicide. Of course i might just be being "offended on someone else's behalf"