So, a while back I bought a book of letters, chosen to show a wide array of interesting people from unusual or unexpected or revealing points of view. Seems like the person who put that together has done a follow-up volume, some samples from which can be found here:
The standout from this latest batch is the first one: Ursula K. Le Guin declining to provide a Foreword for an anthology of stories on the basis that doing so wd make her the only woman to appear in the volume. Her short letter is a masterpiece of economy, making her point politely, forcefully, and memorably.
There's a reason she's always ranked as one of the greats.