"You cut up my rainbow flag T-shirt into HOW many pieces, Rarity?"
This story is an entry for SigmasonicX's Pride and Positivity Contest. All I have to do is enter the contest and come out as not a homophobe, and these charities receive at least $40:
Black Lives Matter - Where to Donate
Support Black People MasterDoc
Transgender Law Center
But you might say, "Is it really worth it to write a story for just a forty dollar donation? You should have demanded more money, MockingBirb!" If that's how you feel, you can donate to those organizations too, to make it more than forty and win the argument. 
Chapters (1)
This was a fun story, but I have to admit, Rarity suggesting that Rainbow specifically use the Nazi symbols for homosexuality felt very uncomfortable. (EDIT: This got fixed). I know Wikipedia claims that modern activists have reclaimed those symbols, but I have never seen them in the wild and the link they cite for this is dead. It's also the fact that Rarity recommends it out of fashion, rather than as a deliberate attempt to reclaim a symbol. If you change that part, I'd be much more comfortable recommending this story to others. Perhaps Rarity could suggest having the rainbow flag just be a part of Rainbow's shirt, rather than the whole thing.
10307921
Shortest answer: Good call to comment on this. I revised out the triangles.
Longer answer: I think my having encountered a lot more gay-positive reclaimed pink triangles in the wild than you have doesn't make my personal experience an available context for every reader. Also, when our story is happening in Equestria, cultural context gets tricker--another reason that I revised the triangles out.
Thanks for your helpful comment!
10307926
Thank you for your quick action!