double standard — any practical question of “is it assur?” should obviously be addressed to a rav/ Posek, not an online forum!
BTW — attending x-mas holiday parties at work is not such a simple situation halachicly –don’t assume that just because frum people do it there are no issues. The individual circumstances of their sha’alah may make a difference. I was told different things different years by my Posek when I had the “December party” dillema, and there were many factors he took into consideration, including whether or not a significant number of the attendees observed x-mas (i.e. was it a generic “holiday party” or a specific “x-mas party”), what the impact to my job would be if I did not attend (including subtle impact on my working relationship with co-workers), whether it took place during working hours or after hours, etc.
If there was no pressing need for you to attend (you make it sound that you just want the free food), I would be very surprised if a rav would give you a heter.