If you're the developer that's your job to tell that to your boss. Come up with analytics to support your findings, make your case, he's probably not going to be reading this thread and staying up to date on all the latest and greatest that's your job. He may be stubborn or you might find out that your user base is all IE6 I don't know but sitting around complaining isn't going to get you anywhere either :)

My fancy looking website doesn't have to look good on somebody's office computer. If they had a good firewall, it would probably be blocked anyway. Also, people still on old IE are used to seeing websites all busted up.