I don't believe that is true. I think most Americans believe the Confederacy was an evil organization that supported and fought for a great evil in the world. This is what most people are taught, and so this is what most people believe.
I think most Americans are glad it was defeated, but again, the reason they think this is because this is what they are taught in the schools, and this message is also heavily reinforced by books and media.
It would have been a only a matter of time before the majority of states joined the Confederacy.
Now this I believe is true, and the possibility this would happen is one of the reasons why Washington DC considered the Confederacy to be a very great threat. There were other reasons why the Washington DC New England power cartel were afraid of the Confederacy, but this is certainly a strong reason why they couldn't leave the Confederates alone.
The result would have been glorious.
I don't know about that. I think Slavery would have continued for another 20-80 years or so, but on the positive side, both the Confederacy and the Union (if they did in fact remain separated) would likely have had far less obtrusive governments.
Not "glorious", but not necessarily horrible, either.
I’ll say it again: Surround the monuments with barbed wire. Then put a fence around it to hop over into the barbed wire. Preventive.