To me this quote means He doesn't have to find a reason to love us. He just does! There doesn't have to be something amazing, wonderful, beautiful, or even holy in us to cause Him to love us. His love is caused by His own heart. Therefore it is not possible for us to change it or make it disappear!
This quote also tells me that God's love is not some means to an end. There is not some hidden reason or agenda behind His love for us. He isn't loving us just to get us to do something for Him in return. He just LOVES us - freely and without any conditions!
His is truly a love "beyond reason."
"He didn't love in order to get something from us but to give everything of himself to us." Eph. 5:1