Have you noticed that none of the sources in the website you posted are after 1984? A lot has changed in the way society views homosexuality since then (thank god).
Take, for example, the line: "Some researchers (eg: Bieber, 1976) claim to have identified abnormal patterns of upbringing and relationships that
seem to lead to homosexuality." No evidence that proves Bieber's claim is provided, and no information is given on who "Bieber" is.
Furthermore, going into the main section of the website, it is entitled "Lecture Notes for a course in Abnormal Psychology Written by David L. Gilles-Thomas, Ph.D., 1989" Again, a lot has changed since 1989. This is neither a current nor scientific source.