Thanks for bringing this up! I, too, was mystified as to why anyone would want to tear down his stature — unless the point was to tear down all statues.
I’ve read his autobiography, but I don’t remember any mention of any owned slaves in there, but it pretty much elides that gap between military services. I have Chernow’s biography in my stack of books to read. Time to move that one to the top, but my ability to zip through books has gone to hell as current events are a major distraction.
BTW/FWIW, for anyone who hasn’t read Grant’s autobiography, I highly recommend it. The only downside is that, after reading it, any other memoir written by a military leader is likely to be disappointing.