You must of missed the posts by haters of the South that have said they wish Lee and Davis both were tried for treason. They are here you betcha.
Objectively he committed the crime, and he also had a very negative attitude after the war which did nothing to help matters.
But Davis wasn't really worth the trouble, and so it was dropped, and I agree with that.
Lee, on the other hand, did everything he could to help rebuild the country.
Trying and executing Lee would have been considered an outrage in the North as well as the South.
It would not only have been unjust, but also extremely stupid.