Many "large southern landowners" obtained their property from the British, who paid them in land not $$$. Washington, Jefferson, etc. were wealthy southern landowners who inherited their land from their fathers, (who had received it from the Brits).
The notion that large southern landowners fought against the revolution to prevent freedom is simply not fact - nobody was more instrumental in fighting against the Brits than Washington, who, when the revolutionary war was going badly (as it did many times), longed to be back at his Virginia home. Our forefathers had slaves - it was a way of life for many landowners. Thomas Jefferson's eloquent writings about all men being created equal flies in the face of how he really lived his life; it's been said TJ owned approx 600 slaves over his lifetime, and his writings about being frugal were also in direct contrast to how he lived his life. Jefferson died in debt and his family had to sell just about everything he owned to settle his debts.