Because God is Just. I take it personally when people give the one finger salute to our Creator, same way I rejoice when people acknowledge Jesus as Lord and Savior. The former have no one to blame but themselves when it comes to their future endeavors.
I completely understand that there will come a day when God's Justice is met, and of course there will come a day when He will tell them that they've made their choice and because they rejected Him, they must be cast from His presence forever.
But I also understand that Biblically, no matter how much people hate and disrespect God, He is looking at them longingly, even to the end, wishing they would change their minds. He might be shaking His head in disapproval at their choices, but how often does He have to do so with us? Probably much more, because as believers, He will hold us to a higher standard.
This, to me, one of the most amazing things about God--that He can take a person's worst hate towards Him and still respond in love.
And, this is what He calls us to strive to do as well.