O.K, x. I will give you a "reliable investigation".
Go to your own Post 98 on this thread.
Next, go to your last paragraph in Post 98 and click on the link you labelled "reliable investigation". On the linked page, under the section labelled "Did Grant's Wife Own Slaves?", go to the third paragraph.
There, in that link you yourself labelled "reliable investigation" you will find the quote:
"Incredibly, Julia brought along one of her slaves on all of her visits to Grant's headquarters during the civil war. When Julia was with Grant, their youngest son, Jesse, was in the charge of "black Julia," the slave that Julia had used since her girlhood. "
With the passage of the Emancipation Proclamation in 1863, Julia's four slaves were set free. It is claimed in the footnotes of her Memoirs that they were not freed until December, 1865, with the passage of the Thirteenth amendment, but this doesn't concur with other primary sources of the period and Missouri's slaves were freed in January, 1865. Grant himself noted that on a visit to White Haven in 1863, Julia's slaves had already scattered and were no longer on the plantation. On extended visits to Petersburg, in 1864, Julia brought along a hired German girl to tend to 6 year old Jesse.
Mrs. Grant may have brought a Black servant on her visits to her husband. I don't know if the servant was paid or not, but it seems likely that the servant would be free to leave on his or her own free will. According to the quotation, by 1863, those who were most willing to leave the plantation were gone. It's unlikely that a servant who remained would be held against her will. References to Mrs. Grant bringing a slave on every visit to her husband, then, would be misleading.
I don't know Mrs. Grant's personal circumstances, whether or how much she paid her help in the last years of the war, or what their wishes were in the matter, but it's possible that, like many slaveowners and slaves, the Grant household was caught up in the gray area produced after slavery was abolished and before wome slaves slaves were able or willing to stand on their own. Condemn Mrs. Grant if you like, but her offense was the same as that of hundreds of thousands of slaveowners. The argument that slaveholders didn't turn out elderly servants to fend for themselves, which has been used in defense of slavery, whether generally true or not, would appear to apply here.
The spurious opposition between Lee and Grant doesn't hold up. Lee was never strongly enough opposed to slavery to advocate actions against it, in his time or for years to come. And Grant never accepted slavery enough to fight for it or to work for its continuance.