I'm sure many here have shared good reasons why they want to throw Santa under the bus, but I thought it might be good to bring a little perspective to the discussion, while at the same time I will officially remain neutral on the subject. The following is from Wikipedia:
Saint Nicholas of Myra was a 4th-century Greek Christian bishop of Myra (now Demre) in Lycia, a province of the Byzantine Empire, now in Turkey. Nicholas was famous for his generous gifts to the poor, in particular presenting the three impoverished daughters of a pious Christian with dowries so that they would not have to become prostitutes. He was very religious from an early age and devoted his life entirely to Christianity. In continental Europe (more precisely the Netherlands, Belgium, Austria, the Czech Republic and Germany) he is usually portrayed as a bearded bishop in canonical robes.
During the Middle Ages, often on the evening before his name day of 6 December, children were bestowed gifts in his honour. This date was earlier than the original day of gifts for the children, which moved in the course of the Reformation and its opposition to the veneration of saints in many countries on the 24th and 25th of December. So Saint Nicholas changed to Santa Claus. The custom of gifting to children at Christmas has been propagated by Martin Luther as an alternative to the previous very popular gift custom on St. Nicholas, to focus the interest of the children to Christ instead of the veneration of saints.
I was raised by my parents with the traditional celebration of Christmas, including Santa Claus, and I seemed to have turned out all right (well, maybe that could be subject to debate). When I was young, Christmas was all about gifts and toys, as I am sure it is for most young children. But a little later, after I had accepted Christ, Christmas was much more a thankful celebration of Christ's birth, and the reason for His birth, which was often brought to mind by all of the Christmas carols.
When I was in my middle to late teens I witnessed the desertion from the church (small "c") by most of the kids that I had known and grew up with in the church, even though the church we attended was a good, conservative, Bible believing church. I think a number of reasons could be mentioned for why that occurred but I don't think any of those reasons had anything to do specifically with Santa Claus.