Other people's bad behavior does not excuse your own bad behavior.
The other day I was forced to have a potentially volatile conversation with someone at work. Before the conversation, I made a conscious choice to be kind and gentle even if we were disagreeing. I believe I did fairly well, even though we did disagree a few times.
After the conversation, someone who overheard it accused me of being overly accommodating, although he used more colorful language to describe it. His argument was that the person who I had been talking to is difficult and doesn't deserve my politeness. Even if that is true, I am not being kind to anyone based on what they deserve, I am attempting based on the kind of person I want to be. How you treat others says more about you than it does about them.
I fail at kindness far to often to point fingers, I just believe that my actions are my own responsibility and I am not given a special dispensation just because the other person deserves my wrath. We all deserve wrath and Thank God we don't receive it. I agree that, unfortunately, that people try to take advantage of those who are kind, but that doesn't mean that kindness should stop. It just means that kindness and gentleness need to be combined with strength and boundaries.
So no, I will not fix your computer. But I love you.