1 Corinthians 10:31
31 "So whether you eat or drink or whatever you do, do it all for the glory of God."
Because we do it in the name of Jesus and are celebrating an actual event that involves Jesus himself. He may not have been born exactly on December 25th, but that is the day that was chosen to celebrate his coming into the world as a gift from God to all of us. We aren't celebrating the pagan winter solstice or the legend of St. Nicholas that both happen to be around the same time. The events really have nothing to do with one another besides sharing the same day. If I visit family and give them gifts (with limits, of course), it's in remembrance of the gift we were given. Since trees aren't inherently evil either, adopting them in the name of Christ isn't a big deal either, to me.
In other words, days in and of themselves, are neutral. It's what is done on that day that is good or evil. The enemy doesn't have the power to defame the birth of Christ. No matter what sins, rituals and/or false worship was being done by pagans on the ACTUAL day Christ was born, whatever day that happened to be, God came with a desire to save everyone and nothing on Earth is greater than God. I can't speak for everyone, but that is what my family is celebrating on Christmas.
Whereas, the activity of Halloween was of evil origin to begin with. The RCC created "All Saints Day" a day AFTER Halloween and I haven't read anything that mentioned they intended to include an evening before. I don't see the good in celebrating the "eve" before the actual day chosen to recognize fallen saints, other than for pagans to keep their tradition alive by renaming it. Reminds me of McDonald's and Burger King. They compete but never cancel each other out. If people did things on November 1st, I could see the reasoning there but most all people recognize the 31st as the official day, while giving "All Saints Day" honorable mention.
The only difference between "trick or treat" now and then is that they didn't have the processed candy and the words weren't meant to be "cute" then.
"All Saints Day" itself involves reference to purgatory and intercessory prayer of people no longer living, which is something I don't believe in, so I can't and won't use it to reconcile Halloween with my personal belief in Christ.