Why do people like Scarborough mischaracterize the Trayvon Martin case?

Joe Scarborough on Trayvon Martin:

I hear he had marijuana in his system. You've seen "Reefer Madness," you know what happens. Really? Really? In 2013, Sean? Come on. Whatever excuse there is to say this young black man had it coming to him, that is the defense. Because there is no defense for shooting down a young black man in a middle class neighborhood with Skittles. Armed with Skittles. . . .

Seriously?  The reason that Trayvon was shot was because he was physically attacking Zimmerman.  Why is it necessary to set up these straw men type arguments?  Whether Martin had drugs in his system or not isn't important, what is important is how he behaved.  The issue of drugs was raised simply because it might make Trayvon's violence more understandable.  Even a prosecution witness, the medical examiner from Sanford, Shiping Bao, thought that the level of drugs in Martin's system could have impacted his judgment.  

Defense attorney Don West also noted that Bao changed his mind on whether marijuana found in Martin’s blood could have affected him that night — the doctor initially said it didn’t, but then backtracked. . . .

But again, the point is the violence, not why Martin engaged in the violence.

For whatever it is worth:

"If you do a Google Search for 'Purple Lean' or 'lean drink' or 'lean drank' it is sort of an urban kind of drug. It's known in some circles as poor man's ecstasy or something like that," George Zimmerman's attorney Mark O'Mara told "The Steve Malzberg Show" on Newsmax. 

"The main ingredients are watermelon, Arizona watermelon juice, a hard candy … for sweetness, and then some type of either codeine tablets if you can get them or Coricidin D, Robitussin DM," he explained. 

"It's an intoxicant and it's a fairly significant one," O'Mara said. . . .