This is literally exactly the same as casting a curse. The three fold law is Wiccan dogma not a law of physics, so there is not bad karma for cursing. This is not even how karma works. Stop being holier then thou!
SMUDGING PRAYER "Negativity that invades my sacred place I banish you away with the light of my grace. You have no hold or power here. For I stand and face you with no fear. This is my sacred place and you will obey.