It's pretty hard not to react that way actually.
At one of the big Cd outlets in L.A. I even went so far as to crowd the guy following me while he was "looking" at stuff as if I wanted to see something in his area
After a while when be backed off I started following him around ..it freaked him out so bad he about ran to the back room lol It was funny as hell because he had been following my every move around the store..
after I bought a couple CDs I headed back through the store to the back door where I always park and this big dude ( about 6'4'' ) came out and tried to intimidate me by staring. I just looked him back in the eyes and laughed at them.
A couple days later I went back and I heard the clerks talking softly...
"That's the guy ..lol ..you should see the footage it's so funny ..blank ..freaked out when he started following him ..and they were both laughing
They don't follow me anymore but that big guy hates me lmao