So yes, giving benefit of doubt is part of interpreting others kindly. I think there's more to it than that, though. We also must learn to judge when we are compelled to draw conclusions about other people's character, and when we are not. We must learn to seek what is good, and that especially includes seeking the good in other people-- rather than trying to uncover the bad. We should spend more time seeking to excuse than to condemn.
You're getting to the heart of it. God looks for any reason to excuse our sins, as long as we are contrite and repent of them. We too, in imitation of Him, need to do the same with our neighbors.
I think too many people equate "kindness" with the modern notion of "niceness", which, in my estimation, is nothing more than flattery. Kindness is carrying out an act in order to soften a hardened heart through goodness and sweetness; therefore, by the way Fr. Faber describes it, bringing others to emulate such kindness, and by this, come to the practice of the true Faith. It's meekness and humility in action. Fr. Faber states:
If they would add a little common kindness to their uncommon graces, they would convert ten where they now only abate the prejudices of one.
"Being nice" is merely offering some flattering words and gestures to make one
feel good, rather than want to
be good. You can be extremely proud and vain and still be "nice" to people.