You can't "defuse" a wedge issue, you can only decline to be manipulated. That is an individual act. There is no "side" to a wedge issue, it is a false dichotomy crafted to create maximal division. They are focus group tested and refined to do so.

The "War on Christmas" effects a greater sense of persecution while framing it as a nonexistent conflict. There is no War on Christmas. I can say Merry Christmas or not, and it will not effect the wedge issue because it is and never was about saying Merry Christmas to others.

I agree with most of what you're saying except for the contention that the dichotomy is false. It's a good wedge issue precisely because it's a true dichotomy. Even when attempting to dismiss the debate as fabricated and pointless, you end up taking a side on accident, flatly stating that there's no War on Christmas and that it doesn't really matter whether you say Merry Christmas to others. On the other side of the wedge, people believe that Christmas is quite literally the second most important day in the world, and fear that we might put our immortal souls at risk if we don't properly commemorate it.