I really don't like the idea that a Tea Party group likened Obama to Hitler on a billboard. That was wrong when the Bush Derangement Syndrome crowd did it routinely, and it is wrong now.
Of course, there are two big differences between then and now. Now, others in the Tea Party condemn the linkage. Then, others who hated Bush simply smirked. And now, the press will be indignant that someone would compare an American president to a dictator and mass murderer. Then, the press didn't seem to care very much and just passed it along without comment when they bothered to cover it at all.
Plus, there's that old line that it is worse than wrong--it is stupid.