Neither slavery nor extermination in itself has to be caused by racism.
According to Thucydides, in the course of the Peloponnesian war, "the Athenians ...killed all the [Melian] males of fighting age they could capture and sold the women and children into slavery. The Athenians then occupied the place [Melos] themselves and later sent out five hundred colonists" (_The Peloponnesian War_, trans. Walter Blanco, NY: W.W. Norton, 1998, p. 231). This fact, however, does not make the Athenians racist.
In contrast to pre-modern & pre-capitalist slavery & extermination (e.g., actions of the Athenians & the Spartans during the Peloponnesian War), racism, (modern) anti-Semitism, sexism, heterosexism, & anti-Communism have the common origin: capitalist modernity. Other than this common origin, however, they differ from one another a great deal, so there is no point in stretching the term racism so as to cover all of the above, since the equation you posit -- racism = anti-Semitism = sexism = heterosexism = anti-Communism = Etc. -- does not help us understand the specificities of any of them.
Yoshie