Things it is not:

Saying "Merry Christmas" instead of "Happy Holidays"
Giving gifts
Giving to charity
Being Christian


Things it is:

Only assuming that all white people that do not 'look Jewish' celebrate christmas
Only saying 'happy holidays' around the 25 of December
[obvious] Having the 25 be a national holiday and not have ANY OTHER RELIGION recognized
Thinking about others only at this time of year
Thinking about 'the poor' as if they are not human
Millions of people excluded from identifying with our consumerist culture who's advertisements focus on christmas celebrators