Ben Witherington offers a fine exposition on both Luke's telling of the Christmas Story and Handel's putting it to music.
The baby lying in the manger reminds us, not of the inherently righteous character of those God came to favor. It reminds us not of the inherently good character of all humanity. It reminds us that in spite of everything we have become, God still loves us, and has provided a means by which we may be saved, if we will but respond to the Good News, if we will but welcome this one child into our homes and lives.
Handel was right when he finished writing Messiah and said 'I did think I saw heaven open, and the glory of God revealed'. Indeed, what redounds to God's glory more than anything else is his salvation plan of other-directed love that includes the least, last, and lost, as well as the first, most, and found. The Hound of Heaven has come down, and is on the loose in the world, in the form of an unassuming, beguiling child. Christmas is for everyone, everywhere--- but will you merely 'keep Christmas', or will you give it away?