It’s not a humrah. Normal Americans (that pretty much leaves out New Yorkers – I”m referring to the vast majority of Christians) consider shopping for Christmas to be part of the observance of how they honor what they believe to be the birth of their diety. Ask you posek:
“Such and such is considered by the majority of goyim to be part of their religious holiday – Am I allowed to participate?” . Unless your posek is uber-Reform, I’ld be embarassed to ask such a dumb question.
Many rabbanim may not be aware that the purchases of presents is part of the Avodah of the holiday of Dec. 25, or that this holiday is truely avodah zarah. That is why we need better secular education in yeshivos – and not from frei Jews. If you hold that Dec. 25 is an avodah zarah holiday, and you realize that most Americans observe this holiday by shopping for and giving presents – it isn’t a shailoh that “Black Friday” is something frum yidden shouldn’t participate in. Do we want goyim to look and say: “Oh, those Orthodox Jews are out shopping for christmas Presents just like us – isn’t it good how they’ve come around to our way of thinking and are honoring “yeshke” (as we call him) by giving presents”.