He had to have at least a few opinions not yet affected by his hatred of Jewish people. Who would he have rooted for in the Cold War? What would be his favorite baseball team? Would he prefer Clint Eastwood or John Wayne? Hitler actually used go on hour-long rants, setting the record straight on anything from opera to architecture to cars. He would have enough free time in prison to weigh in on everything. If Hitler said he loved using Mac computers, would their stock drop, or would it be more like free advertising? Would rebellious kids listen to the same music as Hitler for attention?
At some point, someone would use Hitler's opinion in advertising. No modern politician could resist mentioning his glowing review of an opponent. For the first couple of times, people would be outraged, claiming that irresponsible use of Hitler would lessen the importance of what we learned from World War II. We would all get used to it though. Learning something like the presumed devil-incarnate's favorite chick flick can't be shocking forever. His influence would become a precious resource to those who want to change your mind for their own benefit. It would completely run out when we all have at least one shared opinion with Hitler.