Depends on where you were located, B.A. History. What you were told about it also depends on when you got your B.A. in history.
Re: location, it's true that then, as now, southerners were radically ignorant of the fallout from the racial implications of their assumptions. What I was told about it is irrelevant, though, as is befitting of my education I'm citing primary sources, not repeating someone else's interpretations. Your contention was that suffrage restrictions were in place because men of the time were unaware of any concept to the contrary. It's clearly established by writings of the era that they were, in fact, aware of the possibilities and desires of women and other minorities, ergo your understanding is incorrect.
To be fair, certainly SOME (many?) individuals would not have even considered that any other than white men of property would want to vote, nor would SOME have considered slavery to be anything other than the natural state of things for certain people. But to assert that this was the general logic behind the laws as written in the colonial era is incorrect. Ultimately though, I'm not sure it mattered. We can agree that whether by ignorance of desire or ignorance of capability, the attitudes were certainly a product of their times, and indeed considerably more progressive than that governing ideals of most nations at the time.
(Still not political, but drifting into sociology!)