It's a daunting task admittedly. Even one person boycotting or refusing to use a company's services whose ethics were in complete discord with their own (such as Google in this post, but there are many, many others) is one person more. But you've raise a good point in general, and touched upon a very real reason why so many people don't get as actively involved with Human Rights as they inherently feel that they should be: What kind of difference can one person possibly make?
Siddhartha-The Buddha was one person.
Mahatman Gandhi was one person.
Nelson Mandela is one person.
People have asked me in earnest if I really think I can make a difference with this, and of course I am in no league with the aforementioned above, but is that ever any reason not to do something? I suppose I see it like a forest. One tree does not a forest make, but collectively, a thicket you shall have. If each individual did something - anything - together we could change the world.
And yes, there is always hope.
As long as there's life, there's hope.