How on earth can it be valid if it's evil?
Firstly, you need to distinguish between the rite (which is evil), and the sacrament (which is holy).
Then, you need to distinguish between the “essential rite” (ie., the words of consecration, which as promulgated, are the same in both rites, and therefore not evil), and the “solemn rite” (ie., the prayers surrounding the essential rite, which as promulgated, are evil by defect/omission, for example, by the elimination of the offertory).
An example of “evil but valid” would be the Satanic Mass:
The “solemn rite” is evil for its positive blasphemies, but the “essential rite” is preserved intact, in order to achieve validity/transubstantiation for the purpose of desecration.