Amos repeatedly denied that he was suited or even fit to be a prophet. But he knew what a prophet was supposed to do: notice suffering and bring it to our attention, warn us of the consequences if we do nothing, criticize us for doing the wrong things, take an extreme view to hammer things home, and speak truth to power.
Father Jonathan notes the apt and startling similarity between the prophet Amos and the prophet Martin Luther King. The words and works of both these men was criticized as too extreme and dangerously radical. And we might as well throw Jesus into the same group, since he was a radical extremist as well. An extremist for radical love.