The harm is that it inserts an entity that has no properties, no methods, and no limitations into the causal chain. This is not the way science works.
Oh really? What kind of "harm?" The last time I checked, the properties involved with intelligent design are natural and normal. The details may be more profound or numerous in some places, but they are hardly superstitious. DNA is not superstitious. Understanding it from the perspective of intelligent design hardly causes one to whip out a ouija board, consult an astrologer, and slaughter people in the name of the intelligent designer.
Nor does understanding the physical universe from the perspective of intelligent design cause one to hang up all investigation as if answers are not helpful or necessary. Frankly, evolutionists have absolutely nothing to offer in place of intelligent design that is even remotely useful.