Also later HARM variants also include MMW terminal seekers, beyond that INS/ GPS allows for launch without receiving emissions anyway.
they can just move instead of only turning radar and would still get the job done lol
Current harm has multiple modes.
From self protect
Standard Radar emission mode and Target of opportunity mode.
It also has GPS and IOG guidance. Turning the Radar off would not be enough you would have to move the vehicle too.
The Pantsir wont know what type of missile has been fired and would likely attempt to intercept it.