I think the point of the outrage is probably due to the ‘comments’ that go with the circulation of the photo...
A ‘see, he really is a Muslim’ comment.
As opposed to telling the truth that it was a dress up.
Bill and Hillary were notorious for their dress-ups when they went overseas.
Didn’t even Bush get dressed up in Chinese and Mongolian attire?
Yet they were not also being subject to malicious rumors about the meaning of their dress up event.
That is the reason for the anger, not that the photo itself, but the purpose these evil people are putting the photo to use for.
The outfit dovetails with his past and current associations with the likes of Louis Farakan.