The passage you quoted from Scripture applies to judging other Christians -- whether or not they are living a Christian life or not -- particularly their relationship to God.
We are to be careful is passing judgment on other Christians, but at the same time we must see whether those in our local church are showing the fruits of the Spirit. Obviously we cannot fairly judge anyone posting on the Internet.
However, that passage does not apply to false doctrines and false practices. Celebrating Halloween is a pagan and superstitious false practice, and is not acceptable for Christians, based upon what responsible people have to say. Here is a quotation from history.com:
'Halloween is a holiday celebrated each year on October 31, and Halloween 2020 will occur on Saturday, October 31. The tradition originated with the ancient Celtic festival of Samhain, when people would light bonfires and wear costumes to ward off ghosts. In the eighth century, Pope Gregory III designated November 1 as a time to honor all saints. Soon, All Saints Day incorporated some of the traditions of Samhain. The evening before was known as All Hallows Eve, and later Halloween. Over time, Halloween evolved into a day of activities like trick-or-treating, carving jack-o-lanterns, festive gatherings, donning costumes and eating treats...
This day marked the end of summer and the harvest and the beginning of the dark, cold winter, a time of year that was often associated with human death. Celts believed that on the night before the new year, the boundary between the worlds of the living and the dead became blurred. On the night of October 31 they celebrated Samhain, when it was believed that the ghosts of the dead returned to earth...
To commemorate the event, Druids built huge sacred bonfires, where the people gathered to burn crops and animals as sacrifices to the Celtic deities. During the celebration, the Celts wore costumes, typically consisting of animal heads and skins, and attempted to tell each other’s fortunes...
https://www.history.com/topics/halloween/history-of-halloween
Celtic dieties were in fact evil spirits -- demons -- therefore this basically opens people up to the actions of evil spirits. However, the above should be enough for Christians to shun Halloween.