It Is Not Necessarily That He Is Not Human, But That He Is More Successful

It is not necessarily that he is not human, but that he is more successful than average and therefore has a heavy influence in the world - even as a human, Tommy would be considered a threat.
The film's sense of dread intensifies, and indeed becomes more understandable in its compassionate treatment by Roeg, when Tommy reveals his alien-ness to Mary-Lou. His calm removal of those superficial effects that make him appear 'normal' followed by Mary-Lou's hysterical reaction to her lover in his true form is a moving scene, shows that, similarly to Jack McCann's experience in Eureka, the truth is often what we dread most. This scene is followed by a short sequence in which Mary-Lou's interest in that which has so recently repulsed her drives her to make a sexual advance towards the alien Tommy - indicative of Roeg's constant reminder that we are often attracted by a morbid fascination to those things which also repel us.
Roeg is often found to pervert desire and sexuality in his sociological investigative films. In The Man Who Fell to Earth this perversion is first introduced in the scene where the professor is having an aggressive sexual tussle with one of his pupils, cut with images of Tommy begrudgingly watching a silent violent Japanese dance. Roeg consistently uses such devices to look deeper into the ways our emotions converge at the most fundamental points; how similar sexual desire is to violence and so on. These extreme emotional experiences, where pleasure meets pain, are revisited again and again in such memorable scenes as the aboriginal boy hanging himself in Walkabout after his exhausting courtship dance. Such emotionally punishing, often partially explained, juxtapositions of ideas bring one back to Roeg's comment about science fiction being a way of revealing human frailties. Tommy, the man who fell to earth, experiences a rapid transition from the water revering alien to a whiskey swigging, television addict. Human sins, indeed the seven deadly sins, rear their heads throughout all the films here mentioned and it is not long before an alien is tempted by the desire to experience human debauchery.
It is true to say that Tommy does have a hand in his own downfall, and although he is not conventionally greedy, his ambition certainly drives him on to make more and more money in order to attain his ultimate goal of going home. As with the eventual death of Jack McCann in Eureka, Tommy Newton's fate is finally sealed by others who have been driven to jealous acts due to his ambition and what they can see as his subsequent success. Their greed is manifested in their suppression of his ambition.