You can view the video here. Here is what he said:

“A fraud? No, it wasn’t a fraud,” Clinton said, as the crowd cheered him on. “I’ll be glad to talk to you if you shut up and let me talk.”
When another heckler shouted that the attacks were an “inside job,” Clinton took even greater umbrage.
“An inside job? How dare you. How dare you. It was not an inside job,” Clinton said. “You guys have got to be careful, you’re going to give Minnesota a bad reputation.”

(via)
First Maher and now Clinton, it’s good that the Democrats are standing up to these nuts.