Donald Trump at an Iowa rally on Saturday suggested that the existence of slavery, instead of culminating in the Civil War, should have been “negotiated.” Trump recently hit Nikki Haley with a new insult, saying that he thought “slavery is sort of the obvious answer” to the question about the purpose of the Civil War that tripped Haley up at an event. Now, at a rally, Trump had his own controversial take on the Civil War and how it could’ve been stopped. He started off by saying he found the Civil War “fascinating,” and added that he’s “so attracted to seeing it.” POLL: Should Trump be allowed…