I don't see tantra as "harnessing the power/energy of taboo acts". First, working with controversial subjects like alcohol, meat, sex, theft, lying, and killing is a relatively small part of tantra, I would say no more than 1/10th or even 1/20th, people just tend to exaggerate it. Second, I don't believe these subjects are worked in order to harness their taboo energy, but rather to help the practitioner go beyond some of the deeper-lying preconceptions that may be hiding in the dark corners of psyche easily accessible through controversial means.
For example, if someone has residual anxiety of emotional intimacy and openness, sex may be prescribed as a practice that involves direct open contact with another person. Same with drinking feasts, which may be prescribed as a practice of sincere communication etc.
There is also symbolic/metaphorical component to tantra as @Bakmoon said. In this line of thinking, "having sex with everything that moves" symbolizes "naked" (open, sincere) engagement with the world and "killing one's father" symbolizes abandoning the tendency to self-judge and watch oneself in favor of trusting one's fundamental sanity.