You might walk on the streets of a large city and see a homeless man. You decide to be kind and give him five bucks. Then you go your way. That was kind, but you didn't demand anything of that homeless man. Lewis points out that love is different than kindness.
Love does make demands.
If you showed love to that man, you'd stop and get involved. If you smelled liquor on his breath, love would talk tough. Acts of random kindness are fine, but they are not demanding. Love is demanding. God has loved you from eternity.