But for most of my life the arts did support themselves without government support. I think the arts are important and I support them. I just don't believe that I should REQUIRE you to support the arts either as a person or with federal or state tax money.
And your first sentence is misleading. In the past the arts were not supported by the government, but for hundreds of years they have been supported by wealthy patrons. The Esterhazy family didn't just buy tickets to hear Haydn's concerts. They paid him to sit around and write music. They paid him to perform it for other people. Because they realized it had value. So did, more recently, the Carnegies.
But times have changed. Rock stars and athletes don't support the arts. And for some reason the industrialists of our time typically don't either. So the people of the United States at some point decided that they collectively value music, dance, poetry, etc. and would like to see them continue. We don't want our society to be void of those things. So we decided to put a tiny tiny fraction of our tax dollars toward them.
Now, people certainly have the right to disagree with that stance. They have the right to think that classical music and ballet and theater are worthless and unnecessary for modern life. But no one should act like it is a travesty or unconstitutional that they are supported by the government. To me, the NEA (at least what the NEA should be) is an example of exactly why democracy is great. None of us can fund a symphony on our own. But we take something that we collectively value and we put a bit of our collective resources towards it to see it thrive. And then we get to hear Mozart in the park.