Not just hosts consecrated by "a Christian Church," but specifically hosts consecrated by the Catholic Church is what they're interested in. This i because they wish to express contempt fo God, and God is really, sacramentally present in the form of bread and wine consecrated by the Catholic priest.
The satanists don't want something "symbolic." They want to truly desecrate the Body and Blood of Jesus Christ Our Lord.
Gotcha.
Do you believe some mortal human being could actually desecrate God? I am sure you know they can't.