You do it for yourself, not for others. If your conscience tells you to stand up for someone, then do it. You're not doing them a favour. You're simply doing what your conscience won't let you ignore. So don't expect anything in return. You did it because you wanted to stay true to yourself.
And if your conscience doesn't push you to stand up for someone, that's your choice. But if you do choose to help, don't complain later that you got nothing in return. You weren't doing it for them in the first place. You were doing it for your own conscience.