I dont think the doctor would get manslaughter if it wasnt Michael Jackson - malpractice yes, but all out manslaughter no. Did the doctor force Michael to take the pills, physically restrain him, I doubt it. Did the doctor who subscribed Heath Ledger medication did manslaughter? As far as I know, he/she did not. I'm not going to the level of saying he deserved to die, I'm just saying he unfortunately died, get over it.
On another hand...did anyone catch the 12 idiots who killed themselves over Michael's death? I dont think I would end my life over losing my husband, who I love dearly, but someone I never met?!?