How does Barack Obama say this with a straight face after the speech he gave last night?

President Barack Obama has accepted Rep. Joe Wilson’s private apology for shouting “You lie!” at him on the House floor during his nationally-televised speech on health care reform Wednesday night, but the South Carolina Republican was reportedly resisting demands for more public contrition over the incident.
“I’m a big believer that we all make mistakes. He apologized quickly and without equivocation and I’m appreciative of that,” Obama said in response to a reporter’s question during a Cabinet meeting Thursday afternoon.
“We have to get to the point where we can have a conversation about big important issues that matter to the American people without vitriol, without name calling, without the assumption of the worst in other people’s motives,” Obama said.