How about a Big Bird segment on not stealing from other people?
For adults, Big Bird could go on to say that the problem stems from a social situation, typically called "government," in which some people are compelled to pay for the goods and services enjoyed by others. That it doesn't matter how the government is created or who runs it, or that "most" of "the people" support what it does, it's still stealing from people who wanted nothing to do with funding or spending.
And putting another thing in Sesame Street terms, in the end, while Mr. Snuffleupagus was finally revealed to be real, there is simply no inexhaustible supply of rich taxpayers that liberals keep talking about as the solution to trillion-dollar deficits. Supporting all the Mr. Hoopers, who'll gladly vote for a government that ensures their shops stay open, mean less money to go to the businesses where Gordons and Lindas work.
Here is the entire problem in a Yahoo comments exchange. The Obama supporter's reply is no better depiction of the collectivist mindset, while M's way is that of freedom and truth. If you think something's so good, then you give your own money -- or is it really not that good, that you must force others to give their own money?