"Homosexuality is an unusual sexual lifestyle......Heterosexuality is the norm"

That much, as worded, is a plain as the nose on anyone's face; the majority are hetero, a minority are homosexual.

"The norm" Is a point, or area, on a distribution chart; any characteristic, of anything, is either within or outside any defined range. Whether to stigmatize and denigrate a given thing that is atypical, is an entirely different matter.