Merely being "of pagan origin" is not in and of itself evil. We were all pagan once, and therefore much of everyday life is pagan in origin.
The question is whether it is incompatible with Christianity. Paganism, in its better forms, had much in it that was good and true. That which was good and true was redeemed by Christ. That which was evil and wrong must be rejected. But you can't just reject it all out of hand on the grounds of 'paganism'. That leads to the cultish rejection of much that is good.
But you can’t just reject it all out of hand on the grounds of ‘paganism’. That leads to the cultish rejection of much that is good.
All the “good” things about Halloween are what...costumes and candy???
"Good and true" doesn't have to be redeemed. Other than Christ, nothing is good and true, especially paganism, which rejected the one true God.