If you've spent much time online, you've likely encountered the Activists Who Complain A Lot crowd. Generally well-intentioned, they not only critique a system of oppression, they also spend a large amount of time criticizing the people who are trying to tear that system down. You can find members of the AWCAL in any social justice movement, but LGBT people have turned the technique into an art form.
Practically every day you can find someone on social media or in blog comments decrying someone else on their own side for a minor mistake or perceived slight. They're well meaning, but they haven't quite grasped the idea that no one is perfect. If you're not an actual member of the oppressed group, the target on your back is even bigger and brighter.
Allies also find themselves the target of frequent articles written by academics who like to engage in the age old practice of undercutting progress by talking it to death. Full of words like "oppression," "trigger warnings," and "privilege," these pieces make sure to place the blame exactly where it belongs... the allies who've joined a movement because they want to make a change. They helpfully point out all the flaws of allies, make sure to broadcast that they're not actually members themselves, and highlight all the past mistakes any other ally has made so it can be blamed on everyone.
You know what would be nice to read? Instead of the usual ally-bashing, liberal guilt bullshit, I'd like to read something that actually lays out the truth of being an ally: you will be the least appreciated and most maligned part of a group of people you empathize with and want to help.
Your feelings won't matter. Your intentions won't matter. The amount of work you put in will never be enough and you will never be forgiven for simple mistakes that other "true" members of the group will receive immediate absolution for committing. You will be scorned by academics, reviled by Internet activists, and your contributions will be degraded and downplayed.
And in the end, you will pick yourself up, pull the arrows out of your back, and continue doing the best you can to dismantle the problems faced by the community you have chosen to help. You will put your heart on the line once again for others to stomp on. You will face threats of violence and condemnation by the same people oppressing that community even though it won't be appreciated by most. You will speak up when they can't and be shamed for daring to speak "on behalf" of others. You will screw something up and be vilified. You will carry on doing the best that you can because you are a good person and while some like to claim that intentions aren't important, you will know that without good intentions nothing evil would ever change.
You will remember that the Golden Rule is the one constant of every religion because of its simplicity and, well, good intentions. And you will know that you are doing the right thing because it is the right thing to do. You don't need the approval of liberal hypersensitive Internet activists who don't actually do anything other than complain about the work of others. They are not the people who want improvement; they crave the attention that being oppressed gives them. They want you to fail so they feel better about themselves.
You do it because it is the moral thing to do - and no amount of Internet savagery or academic mumblings will change that. You're an ally.