He mentions "Let America Be America Again", but the lines quoted are from the poem "Goodbye, Christ", which you can read in full here.
It was a pro-communist poem. So what? It was published in 1932, by a black man. It's not hard to imagine a black person in 1932 being a bit disenchanted with the United States and capitalism. And, in theory (as the saying goes) communism sounds pretty good to the oppressed.
It's not like this was written in 1965, when we knew the horror that had been Stalin, and that in practice communism didn't work out too well.
You have to read things in context, which this college student with a slight grasp of history obviously did not.