It's not our job to play judge and jury, to determine who is worthy of our kindness and who is not. We just need to be kind, unconditionally and without ulterior motive, even - or rather, especially - when we'd prefer not to be.
It really shocks me when I encounter people who think kindness doesn't matter. Because I think it's pretty much the only thing that matters.
Kindness is not about instant gratification. More often, it's akin to a low-risk investment that appreciates steadily over time.