Um, ok. I didn't know that Christians, by saying 'Merry Christmas,' were hording all the joy for themselves. Wow, no wonder people get angry when someone says 'Merry Christmas.' They hear, "I'm a Christan and I've come to steal your joy!" That's horrible. This is just more proof that the true message of peace on earth (everyone on earth), good will to men (and women -- everyone) has not been well presented or people wouldn't have such an incorrect view of Christians.
When people say 'Happy Holidays' I don't think they are trying to take something away from me. I think of it more as a question, as in, "I don't know what holiday in particular you're celebrating, so I'll just wish you 'Happy Holidays.'" At which I respond, "Merry Christmas!"