I don't know if he did or didn't. My point is that George Washington--a towering collossus--did in fact free his. That puts him--as if there were any question--in much better standing on the question than, say, Thomas Jefferson, who pawned his off to cover debts, or Robert E. Lee, who chose to fight against the USA in defense of an illegal confederation predicated on the perpetutation of slavery. But heck, we all make mistakes. As you judge others, as the saying goes. I am sure General Lee was in many ways a great man. I wish him the best. I'd rather have my troop named after General Washington.
Slavery, like it or not, was constitutional and had been protected by the courts as such for nearly 100 years. Had slavery been an issue, the southern states would have had recourse through the existing justice system.
The power of taxation, which Lincoln had made clear would be used to subjugate southern agrarian interests to those of northern manufacturing, was a constitutionally delegated power of the national government.
Avoiding abuse of that power required secession.