This is quite thoroughly disproven by the words of the Founders themselves, including those of Patrick Henry quoted upthread. Had they considered blacks to be less than men, there would have been no reason for slavery to bother them. And it most certainly did.
Most Americans didn't care much about it, and to the extent they gave it thought, disliked the institution while at the same time considering blacks inferior.
We should keep in mind that the "science" of the time pretty nearly unanimously concurred in this opinion. The only people who considered blacks fully the equals of whites were the occasional fanatical Christians who took their Bible seriously. Unfortunately, they were counter-balanced by other fanatical Christians who used other passages to "prove" that slavery was God's eternal will.
Over the course of the 19th century this consensus split. More and more in the North became opposed to slavery and especially to its spread. More and more in the South began to think of slavery as a positive good that could and must be spread over the Earth.
The first group tended, though not universally, to think of blacks as something approaching equals. The second group displaced them down the scale, to being less than men, as you say.
What you are doing here is displacing in time the attitude towards blacks common in the South of the 1850s back to the 1780s and making it the norm across the country. Which historical legerdemain Taney also tried in Dred Scott, but which was diced, sliced and dismembered in the dissenting opinions.
You misunderstand the attitude of the South. They knew it was evil... it was just a necessary evil for their way of life. They didn't think it was a good thing that should be spread everywhere. They wanted new territories and states to be slave states not so the "good" of slavery could be extended but so they would not be crushed by an increasingly abolitionist Congress. They were trying to maintain a balance of power not argue for slavery's virtues.
Wrong again. I didn’t say everyone believed that. Cherry picking does not make me wrong. It was the predominant view when slavery in America started, which explains why it was practiced in almost every colony. Even if I was wrong, racism as defined today has no relevance to what was going on with slavery.