Quite simply, it is an abbreviation for
Sick Mother Fucker.
Such a person is despicable and warped and does things no sane or decent person who do. Also, "SMF" is an 1984 song by Twisted Sister. The song's words do not explain what the abbreviation means.
Slobodan Milosevic's generals are responsible for the rape, mutilation and sadistic sexual bondage of women and girls, as well as herding men and boys in concentration camps where they were forced to do sex acts on each other, drink piss and eat shit. The males either starved or were beaten to death. Numerous gross abuses were commited under Slobodan's orders. He and his military leaders are war criminals as well as a bunch of SMFs.