Here's my effort:
Dear Mr. Stumpf:
It may come as a surprise to you, but there are people in the United States who actually love and cherish this country. They believe that the American Flag is a great symbol of the values of our precious freedoms, including freedom of speech. At the heart of America's history as a beacon of hope to the world, lies the fact that we maintain a sovereign nation within distinct borders and that within those borders, her citizens are protected by the rule of law.
Now you and others have come along to spit on this heritage and to undermine the freedom, the liberty and the hope that the American flag has stood for at schoolhouses, at courthouses and on battlefields since the founding of the Republic. You exhibit disdain for the many who shed their blood under that flag for all it represents. I looked everywhere in the Constitution, the Declaration of Independence and our other founding documents, and I couldn't find a word about multiculturalism or any other post-modern stupidities suggesting that we should do away with our flag, our liberty or our sovereignty as a nation in the face of a wave of illegal invaders (yes, I said illegal).
You have no place teaching the young people of this nation. Your ideas are quite literally subversive to the United States of America. You should resign immediately. Failing that, if there is any common sense and true patriotism left in your school district, you should be fired immediately.
Good day, Sir.
It's a good letter. Send it out.