Millennials and Zoomers/Centennials (and probably the Alphas, once they eventually come-of-age) are definitely open about discussing sexuality freely. As an older Millennial, I feel like the "proud papa," in a way -- beaming, as I wish my own classmates when I was in K-12 could have so openly lent me such support.

Just speaking for myself: if I had a straight friend or relative who posted a profile pic of themselves raising the Pride flag, illustrating that they're an ally to the LGBT+ community...I wouldn't consider it to be appropriation. I'd be proud of them!