Would the message of the poem change if it were writen in free verse?

Phillis Wheatley's poem "On Being Brought from Africa to America" would have the same message if it were written in free verse, but the tone might change and the central idea may be more threatening without the rhyme scheme. 
The poem's rhyme scheme is aa bb cc dd, which is a very typical and basic rhyme using couplets. The rhyme scheme gives the poem a sing-song quality similar to children's nursery rhymes. The poem is reproduced here:

'Twas mercy brought me from my Pagan land,
Taught my benighted soul to understand
That there's a God, that there's a Saviour too:
Once I redemption neither sought nor knew.
Some view our sable race with scornful eye,
"Their colour is a diabolic die."
Remember, Christians, Negros, black as Cain,
May be refin'd, and join th' angelic train.

If you read the poem aloud, you can hear the lyrical but simple quality of the rhymes. This rhyme scheme works to lessen the intensity of the subject matter. 
 
Wheatley begins by saying that she was blessed to be brought to America from Africa, as she has become Christian and has repented her "Pagan[ism]." She implies that learning about God and Christ have had a positive impact on her and that she was, figuratively, in the dark about the error of her ways. 
 
In the next four lines, however, Wheately's message becomes more pointed as she tackles racism and inequality. She refers to "some" who think African Americans are inferior and who associate black people with the devil. She says that "Negros, black as Cain" can also be redeemed through Christianity. The subtle undertone of these lines is that Wheately believes African Americans are not inferior and certainly do not fit the stereotypes white Americans have placed upon them. She uses the common belief in Christianity to make her message more appealing to her white readers. However, the idea that, in this early period of American history, white citizens would accept black citizens as their equals would have been controversial. Using the aa bb cc dd rhyme scheme makes the message softer and gives it a less extreme tone. Free verse (no rhyme scheme) may have come across as more aggressive or straightforward.