It doesn't fix anything directly, but it's an easy, effective way to show support for people who have been disenfranchised.

And it's the sum total that counts, so every little thing makes a difference. One project making changes doesn't have much of an impact, but if every project on GitHub did the same that would be a very clear message the tech industry isn't satisfied with the status quo.

Sometimes all it takes to stop a bully is for one person to speak up because then others that might have been keeping silent will feel more comfortable speaking up as well.