Refs target Perk because he has gained a reputation early in his career as a guy who can't set a good pick, as well as a guy who can't control his temper.
Fair or not, it is incredibly easy to get a reputation in the league from the refs, and it is just as hard to get rid of it.
While it may be unfair, this is simply how the league works, and for every negative call Perk gets, Pierce, Allen, and KG gets a positive one because of their reputations. Even Sheed gets away with a lot of contact on defense that other guys do not get away with, because he is known as a great defender.
Now, with the technicals, it is a problem with Sheed and Perk. But unfortunately, they did a lot to bring it upon themselves. They have both made a career of showing up refs and complaining non-stop. If they can't see how that makes them a target for quick T's, then I don't know what to tell them.