If you can't see the image, it consists of a photocopied picture of soldiers in combat, over which someone has drawn rainbow stripes, and pasted the text:
I thought gays fought to promote tolerance of differences thus the rainbow flag representing their acceptance of diversity. Seems like fighting and killing are the exact opposite of promoting tolerance and diversity.
Where to begin...
First, there's this thing called Wikipedia, where you can look up the origins and significance of things like the Rainbow Flag. You know, just to make sure you've got it right. As it turns out, it doesn't represent that gay people have "accepted diversity" so much as the diversity of the LGBTQ community itself. A bit of a difference there.
Second, gay people have not made it their job to "fight to promote tolerance of differences" in every way. Because there is no representative Council of Gay that decides what gay people are going to do and what they stand for.
Third, even if someone is a pacifist, that doesn't mean that they're down with discrimination in the military. Being able to defend one's country is an important part of asserting equal citizenship.
Seriously, I think the rainbow imagery has some people confused into thinking that LGBT folks are all magical happy people filled with peace and understanding. Note to postcard writer: "gays" are just people.