This was a really interesting perspective to read. A lot of this was eye-opening and did get me to think a little more critically about my own stance about flags. Personally, I don't feel the need to wear all of my causes on my sleeve. (There's a South Park episode that addresses this issue well.)
But on the other hand, I understand the resistance to the American Flag's sheer all encompassing-ness. On one hand, I think there's an elegance to being able to say, "Look, we're not a perfect country, but as a whole we've got a lot to take pride in." But on the other hand, I think there are things America does from time to time that are so atrocious that there is a sense of shame in that flag. When Trump was elected president, and when he was acquitted after both impeachments, those were each incredibly unproud times to be an American. I took no honor in that flag.
I thought of a music-related analogy to the flag situation. If you're a fan of a band, many wouldn't simply settle for showing that love with a shirt that says "I love music!" They'd sooner buy a shirt for that specific band to send a more pointed message to whatever friend or stranger might see it.
I can see a practical reason that our political beliefs could come back to haunt us more than our musical preferences, but I do also think there's a certain value in more explicitly proclaiming which things we do and don't support. Especially before gay marriage was passed or slavery was outlawed, I can absolutely see why a gay or black person wouldn't see an ally in American flag. And inversely, I can see why a gay person would see a friend in that rainbow flag.