The institution of slavery was thousands of years old before the founders were born.
The institution of slavery existed on these shores before the first European ever set foot here, as it did in the rest of the world.
Slavery did not originate with the founders.
Because slavery did not originate with the Founders, they did not impose (v, to establish, force or inflict something on someone) slavery on anyone.
For those sold in bondage on these shores, the imposition of their status occurred before they were loaded on the boat (they were already slaves when they arrived, only their ownership changed).
The Founders did not do that.
What the Founders did accomplish was to lay the foundations of a government based on human rights which eventually abolished the institution of slavery.
Blaming the founders for slavery makes as much sense as demanding reparations for the institution from people who never owned slaves, and in many cases, whose ancestors were not even here at the time the practice existed.
Fixed for readability
One does not have to originate something to impose it. The laws against murder were not created by the founders but the US IMPOSED the legal sticture against it.
o·rig·i·nate
1. to take its origin or rise; begin; start; arise: The practice originated during the Middle Ages.
2. (of a train, bus, or other public conveyance) to begin a scheduled run at a specified place: This train originates at Philadelphia. verb (used with object)
3. to give origin or rise to; initiate; invent: to originate a better method.
Collins English Dictionary - Complete & Unabridged 10th Edition
VS
im·pose verb (used with object)
1. to lay on or set as something to be borne, endured, obeyed, fulfilled, paid, etc.: to impose taxes.
2. to put or set by or as if by authority: to impose one’s personal preference on others.
Dict.com