I'm sure you've heard that saying, "It takes more muscles to frown than it does to smile." Science is still not exactly sure how many more muscles it takes to frown (most estimates seem to be around 3x's). Still, the number really isn't important. What matters is the amount of effort it takes to come across badly, verses coming across good. And, this saying isn't just true of facial expressions. I've noticed that it's true of how we treat others as well.
It's harder to avoid than it is to acknowledge.
It's harder to snub than it is to support.
It's harder to maintain a lie than it is the truth.
It's harder to live life feeling sorry for one's self than it is to be content.
It's harder to be bitter than it is to be joyful.
It's harder to maintain power than it is to share.
I could keep going, but you see my point.
It's too hard to maintain a frown. It's too much work to always avoid a brother. I'd rather just go the opposite direction and live a life of redemption, true forgiveness, and peace. It's not really about Christianity (although that's a good reason too). Rather, being kind just sounds easier to me.