These lines were spoken by Booker T. Washington in his famous "Atlanta Compromise" speech. They mean that the fate of the oppressor is bound together with those whom he oppresses. In the speech, he mentions how the oppressed negro people will become a dead weight on white society. If they will lift up their black brothers, they themselves will be lifted up. But if they continue in their "sin," then the "suffering" will come to them as well.
As an example, he mentions the amount of crime committed by blacks in the South, a result (he posits) of their oppression. If you would not be scared of the criminal, remove from him the purpose of his crime. One will always fear the person, or people, he is grinding under his heel. One need not fear a brother.
abreast - side by side The parade had six drummers marching abreast.
Being abreast means being side by side.
draw abreast = gleichziehen
The origin of abreast is late Middle English: from A- 'in' + breast.
The brass band passed by, marching four abreast.
We have been abreast of this situation for a time now.
I have information here to keep you abreast of the situation, sir.
The president wants to stay abreast of the most recent developments in Libya. OR The protest marchers walked arm-in-arm, five abreast down the street.
Together
uniform
Along side at the same level (think of runners crossing a finishing line "breast to breast" they are abreast of each other and finish at the same time).
it means walking side to side