You are using schematics here. You know there is a G-d based on your faith that there is a G-d. I can say the same thing as I KNOW there is a G-d and that Jesus was the Messiah He sent to us... But it is based on faith, in both of our cases.
No, they actually are not... THEY even say they are not...
In all of my studies, including in Greek and Latin, it was not and is not acceptable to most main line Christian belief systems. If you put Xtians, XMas, you are taking Christ out of the equation which is not acceptable to most Christians. It is offensive to me, and many people I asked about it of this past two weeks... It feels to me as if you (general you, not you specifically) are afraid to say Christ in such things as it might be real, and you don't want to make it real... And because someone creates a web site called xtians.org doesn't make it not insulting. It just means the people that created that web site (and if you log in and dig into their site, it is not overly Christian centric) felt that using that name was acceptable.
I don't have their contact info on this computer, but when I get my other laptop back I will.

(Not sure why it matters though....)