"x" in xmas goes back to a time when most people were illiterate, back in the middle ages and thereabouts
Christians would use "x" in xmas to show these non reading folks that the "x" represented Jesus Christ
the pilgrims actually banned Christmas
it really was not celebrated to much extent in America until mid 1800's
as you say, some of it's origins are pagan, but Christianity did take over the holiday, and much of how it is celebrated today
it really not a bad thing