It's easy to imagine what would happen.
Life and commerce in big cities would come to a standstill, because drivers would stop at green lights everywhere and motion the drivers stopped for the red light to go through. “Go on through. I don't want to slow you down!” they'd shout. “We'll all get along better this way!”
And can you imagine what reality shows would be like? Dullsville. Everyone would be nice. They'd share food and help each other in the competitions and wouldn't say nasty things about other competitors. “No reason we have to be that way,“ these new contestants would say. “We can all win! And have lots of fun, too! Let's just get along here!”
And juries would have to acquit all defendants. How could a jury member who is like Harry Reid believe that anyone could do anything as horrible as whatever the defendant was charged with? And, of course, if someone did happen to do something as heinous as whatever it was they were charged with, everyone would believe that they have learned their lesson. So why punish them further? “Let's get along here! To judge and punish them is to look backwards, not forwards.”
That would mean prosecutors wouldn't have much to do, either. But they wouldn't want to do much, if they were like Harry Reid, because they just would be totally unable to believe that anyone would lie to them. “Why would anyone lie to me? We're just trying to get along here and help each other build a better life for everyone!” is what they would say. So after asking their suspect a few questions about some double homicide or a bank robbery or embezzlement and listening to the suspect say over and over, “I don't know anything about that!” they'd let them go.
Lots of other things would change, too. News shows would be filled with even more stories about miracle weight-loss treatments. Major league pitchers would make sure every batter they faced got a good pitch to hit – “We'll get along so much better if we all hit the ball hard and far!” Bosses would give everyone raises. Meteorologists would never predict rain or hail or even cold weather. And scientists would side with food companies and chemical corporations and say it's all good for you, eat what you want, no reason to be moderate in anything.
All in all, it would be a good life. Even the Republicans would be fun to talk to, except, of course, they'd still be insane.