If you really want to show your support for Christianity, then instead of rushing out to give your money to Chick-Fil-A (who does -what!?!- with that money), why don't you go out and make a donation to a Christian organization that is actually doing something good for your community?
I'll give an example for my Parkersburg peeps - The Old Man Rivers Mission. They are a Christian group helping to clothe and feed the homeless in the Parkersburg area. You can find similar organizations like this in your area - all you have to do is look for them.
Make a donation to a local Christian group that is sowing some good in this world instead of lining the pockets of some CEO. You reap what you sow so let's do something that will improve the quality of life for people in need!