I respectfully disagree. "Must have" and "I believe", etc., constitute speculation, which isn't necessarily a bad thing when there is nothing else to go on. However, in the case of General Lee there is no need for speculation. Lee was a gentleman, as you said, and a gentleman does not use inflammatory language. But another mark of a gentleman is honesty. Bear in mind that Lee's correspondence was written mostly to family members, to whom he was explaining his decision to resign his army commission and cast his lot with Virginia. As the patriarch of his family, his knew his actions would greatly influence the actions of his sons and nephews, as well as his friends. Lee recognized that heavy responsibility, and therefore spelled out his decision honestly and completely. You should read his correspondence, if you have not already done so. I think it will put to rest any suspicions you may have on ulterior motives.