You're making a big leap here - not everyone who wears dark clothes is depressed, or being made fun of; plus, you've been given one photo of the guy, and in that one photo he happens to be wearing black. For all you know, he wears pink on Mondays and polka dots on Thursdays. I think people are upset with you because it feels like you're making a lot of assumptions based on a very fragile view of this mans psyche. It's rude, really; you don't know him well enough at all to judge his mental state based on the color of his clothes.

Also, shelters/rescues/ and especially emergency rooms are going to be places you would want to check anyway, regardless of what this persons mental state currently is. You simply never know, and if there's a chance he could be taking some kind of shelter in one of those places, then by all means call.

Finally, it wasn't /u/undrtow218 's "inferiority complex" that led him to infer anything. While they may have been wrong about your assumption, it doesn't mean making another assumption about someone else in any way rights that wrong.

One of my biggest pet peaves are armchair psychiatrists, who go about judging others' mental states and well being, and giving their own haphazard diagnosis out like candy. You end up doing so much more bad than good, in the long run. Please stop assuming anything about a person's mental health, especially when you have practically zero concrete information to go by.