What two classes of people are mentioned in the poem?
In Edwin Markham's poem "The Man with the Hoe" the two social classes of people mentioned are the labor class and the land-owning/ruling class.
The central conceit of the poem is that the man depicted with a hoe has been reduced to an unthinking, unreflective animal state that is far removed from his natural or intended noble state as a human being. The farm laborer is called the "Slave of the wheel of labor" in the poem.
"What gulfs between him and the seraphim!"
The distance between the agricultural laborer working as "a brother to the ox" and the angels of his higher nature is attributable to "the world’s blind greed," which is represented by the wealthy class that exploits the laborer.
O masters, lords and rulers in all lands,
Is this the handiwork you give to God,
This monstrous thing distorted and soul-quenched?
The labor class is shown to be reduced to an unnaturally low state of spiritual and political being and the ruling class is shown to be immorally willing to create and perpetuate this indignity.
The poem's distinction between these two classes of people is highly political and the poem espouses an inevitable revolution that will correct for the loss of the laborer's dignity. The labor that is said to be responsible for making kings and kingdoms into the glorious things that they have become and one day that labor will rise up and overturn a corrupt world order. The poem implies that this is true because the status quo -- a situation of disparity and exploitation -- robs one class of its divinely endowed dignity and this unnatural state of affairs is bound to come to an end.