I don't really consider it an exploit. It's tactical.
Thus, when I see something like this in-game...I just change tactics myself and try to use it against them.
I pick a decent angle, and fire at the decoy, drawing out the offender (who is often times using the spray to draw noobs into firing, letting them know they're coming). But I'm not on the expect vector, and I usually get the drop on *them*.
Then you get to gloat more.

mrC