Question

why did the spirit in the Ouija board call hallock a traitor

Answer 1

the spirit of Ouija board called Hallock a traitor because hallock promise to ghost Helen to that he will not use Ouija board again

Answer 2

The spirit in the ouija board call hallock a traitor because hallock had promised to the spirit that he would stop his friends and family to use ouija board to call spirits for unwanted reasons but now he is using the board himself.
Hope this will be helpful :)