Particle physics and knowing particle physics is, and has been of direct military and economic benefit to our society.
But it is the principle of the thing. Are we going to have the best and greatest particle accelerators here in the USA, or are we going to send our smartest physics graduate students to Europe?
In the immortal words of Robert (Bob) R. Wilson....
“It has only to do with the respect with which we regard one another, the dignity of men, our love of culture. It has to do with: Are we good painters, good sculptors, great poets? I mean all the things we really venerate in our country and are patriotic about. It has nothing to do directly with defending our country except to make it worth defending.”