First, a distinction: I would much rather people use rainbows and pink triangles than HRC logos when they refer to the wider LGBT community. The main reason for this is that they are highly recognizable symbols... it's difficult to hide your queerness behind a rainbow. Also, I'd be a hypocrite if I said you shouldn't use them, because some of my favorite designs involve rainbows and triangles, and I still use them.
Unfortunately in several ways rainbows have been tainted by corporate pride for me. I enjoy pride events, but after a while I just associate them with people trying to sell me rainbow shit, and if there's anything symbolic of the ugly side of the LGBT movement it's sweatshop produced rainbow shit.
The worst, though, is pink triangles.
Not because people use them. Pink triangles are an extremely powerful and historical symbol... as a Pagan Warlock I attach huge importance to symbols, not only on a human judgmental level but on a religious level. This is a really powerful symbol of reclamation. And it's like nobody in my peer group actually knows what it stands for. I'm not shocked, but I am appalled by this... not at the people who don't know, but at the fact that we've gotten to a point where there's that little awareness among us. I took a queer trivia quiz five or so years ago and "Where did the pink triangle come from?" was one of the questions labeled "difficult."
Short history lesson: Most of us (at least I hope) learned in high school or earlier that Jews during the Holocaust were made to wear yellow Stars of David on their clothing. My own textbook had a table that listed several other symbols widely used in concentration camps, most of which were color-coded triangles. So the Roma community got a brown triangle, political prisoners got a red triangle, Jehovah's Witnesses got a purple triangle, "asocial" people got a black triangle, and "sex offenders," mostly men who had sex with men, got pink triangles.
This symbol was reclaimed, likely after a book was written by Heinz Heger that detailed the experience (it inspired the play and movie "Bent," if you've seen either of those) and made the symbol's nature more widely known.
When you use this symbol, acknowledge its deep and dark history. Know when you wear it that you are carrying on a memory and a legacy that goes beyond gay bars and corporate pride events. You are saying more than just "I'm gay" or "I'm queer," you are saying "Thousands of people died without having the opportunity to live the life I live today." Because if there's one thing that frustrates me, it's LGBT and queer people who do not understand that our ability to even speak about our sexuality grew from decades of systematic and often deadly persecution, and that's where this symbol comes from.