I was thinking that too, nothing against Harleys or anything 
but I know my neighbor after the state inspection happens, slips on the straight through pipes and I never see Harleys pulled over for straight pipes but a muscle car would.... 
Top 10 reasons why cops pull over loud muscle cars, but not loud Harleys...10. They are more likely to get shot pulling over a Harley.
09. They cant causally look inside a Harley to see something else they can arrest you for.
08. They want to check out the muscle car, and tell you about the one they have/used to have..
07. You see one Harley, you pretty much have seen them all.
06. Chicks that drive muscle cars are nicer than chicks who drive Harleys.
05. They get confused by license plates mounted sideways.
04. They may have to help push the Harley to get it started again.
03. You can see the pasenger on the Harley.
02. Muscle car drivers smell better.
And the number one reason why Cops pull over loud muscle cars instead of loud Harleys...01. There are no donuts laying around on the back seat of a Harley.
BTW: NO OFFENSE to muscle car drivers, Harley riders, or Cops. I have respect for them all. Just having a little fun because I have WAY too much time on my hands.
