Alexander may have been many things but there has never been any credible proof to suggest he was bisexual but that doesn't stop the homosexual community in its attempt to re-write history. There is plenty of evidence of homosexuality throughout history usually in the form of young men (many times slaves) being taken under the wings of older men. The unflattering history of homosexuality, much of which would be considered indistinguishable from molestation and abuse if today's standards were to be applied, is treated as if it never existed.
In a sense, we cannot apply today's standards to those of the old. If we were to do that to history, we would be revisionists ourselves. Whils there may be no "direct" evidence showing Alexander's sexual orientation, males would tend to have a wife for "making babies" and another male "for pleasure". Seeing how it was even more commonplace amongst soldiers (almost as part of comradery....that, and the lack of female companionship on decades-long conquests), an educated guess can be made as to Alexander's sexual life. His (assumed) actions, if anything, were fairly protocol for the time. And his spreading of Hellenistic culture did, in many ways, bring said institution to Rome.