Christmas reminds me of God's goodness. He sent his son, Jesus, which proves his goodness for all time. Through Jesus, we are given the gift of transformation into new men and women. Over the ages, millions have testified as to the power of this transformation. I am also witness to it; Jesus changed the direction of my life and I am both more joyous and happier for it.
Atheists deny the reality of God, but the testimony of millions belie their claim. A militant atheist is someone who claims that God does not exist and further claims that all the problems of the world are His fault.
On a lighter note, it is also said that beer is proof that God loves us, as if we needed more, proof that is.