Because it’s a shame, and they know it - especially if this bizarre climate is just a blip and things go back to normal. Then they will have demolished what was once a fairly impressive display of patriotism for nothing.
Patriotism, like the flag and so many other things, have become blunt weapons wielded poorly. I'd rather have a show focused more on "We the People".
Either way, Lincoln's speech should be heard by both audience and those on stage:
"This government must be preserved in spite of the acts of any man or set of men. Nowhere in the world is presented a government of so much liberty and equality. To the humblest and poorest among us are held the highest privileges and positions. What constitutes the bulwark of our liberty and independence? It is not the frowning battlements, or bristling seacoast, our army and navy. These are not our reliance against tyranny. Our reliance is in the love of liberty which God has planted in us. Our defense is in the spirit which prizes liberty as the heritage of all men, in all lands everywhere. Destroy this spirit and you have planted the seeds of despotism at your own doors."
"At what point shall we expect the approach of danger? By what means shall we fortify against it? Shall we expect some transatlantic giant to step the ocean and crush us at a blow? Never. All the armies of Europe, Asia, and Africa combined could not, by force, take a drink from the Ohio or make a track on the Blue Ridge."
"At what point then is the approach of danger to be expected? I answer, if it ever reach us, it must spring up among us. It cannot come from abroad. If destruction be our lot, we ourselves, must be its author and its finisher. As a nation of free men, we must live through all time, or die by suicide. Surely God would not have created such a being as man, with an ability to grasp the infinite to exist only for a day. No. No. Man was made for immortality."
