A good example in Tumblr Art is the prominent feature it's a gross fetisization or stereotype of a minority, but there can be other factors like the message or style that flags attention.
More on topic and more "Art Critic" Val, comin' straight at you: Crippled legs, vitiligo, huge scars, albinism - these are all fun traits to draw in a character, but they should not form the basis of all your art or a character. MANY of these people rely on purely luck-of-the-draw afflictions, quirks or traits to make characters interesting. If the only defining trait is an quirk, sexuality or injury and no other substance to them they aren't really more then a prop piece; and if someone calls out this one dimensional character, they are simply called bigoted and wrong.
All these artists appealing a guilty complex or a cheap way to appear as sanctimonious as possible.