We're used to having "think" take a preposition -- "think of," "think about" -- or having the object of thought be a clause with "think that ....," but the verb may have a transitive sense of forming a mental picture, and in that case, it can take a simple direct object.
The OED gives a nice example from William James:
We think the ocean as a whole by multiplying mentally the impression
we get at any moment when at sea.
That is, we understand the immenseness of the ocean by gathering all the glimpses we get of the seascape when we're on an ocean voyage.
Your quote is from a piece about John Hammond, a music producer responsible for promoting the careers of many black musical artists from Billie Holiday to Aretha Franklin. Hammond is described as forming a mental image of the American musical scene and considering it an "outrage" that black musicians were denied the credit they were due.
thought (verb) it (direct object) an outrage (objective