It isn't the "paganism" that we are comfortable with. The symbols of Christmas are secular: Santa is the diminution of a bishop of Smyrna and not at all ecclesiastical any more, so he is secular. The tree has no one dancing around it and praising and thanking the earth or the earth goddess any more (except perhaps the occasional Wiccan whose religion is far more modern than they like to think), so it is secular. Even the solstice is noted generally only as a time of the daylight finally lengthening which means that summer and vacations will finally be here.
The question of this thread I think was misdirected. It's not that we are comfortable with paganism. We're merely comfortable with anything no matter its origin if it is stripped of its original meaning (we don't spend much time on Christ-mass morning worshipping, do we?) and made harmelss so we can celebrate something and enjoy ourselves. We will turn anything into entertainment if we can, and we've done that with Christmas, the bunnies and eggs of Easter, the ghouls of Halloween, and largely the fireworks of the Fourth of July. As long as we can have our corn on the cob and barbeque, other people can sing about Valley Forge all they want. We like our firworks.
It isn't paganism. It's the fun we like.