The Supreme Court is not always right and includes political factors in how they decide cases. Also someone who likes Palin does not think a Palin retirement fund is necessary and someone who hates her would not donate money to it. And someone in the middle would not make a fuss over something or think it is a funny joke.
No, the Supreme Court isn't always right, but they are always the last word. And, their last word on this subject is speech and money aren't interchangeable values or commodities. And, I wouldn't want to rely on the IRS getting my joke.
In many cities (perhaps Chicago), there are fairly strict rules about how TIP charges must be displayed as well as other collection jars - I'd wager that Chicago has such regulations and this TIP jar probably violates them.
Lastly, if this was an insult directed at Obama, I don't have any doubt that his minions would bring the full weight of the controlling government agencies on the perp.