Incest is an abuse of power. The incest, though, is more than physical abuse as it can include emotional or psychological elements. From ancient times, incest was shunned for its effect on the family and more widely on society. For the ancient Athenians, incest had political consequences as they saw the polis as an extended family.. In political terms, incest would be a way to describe tyranny. The tyrant, acting as the city’s patriarch, had a disordered eros as the city served his interests and the normal relationship between ruler and ruled was corrupted. In the medieval era, incest by the father was described as a domestic tyrant.. The father corrupted the family by his incestuous relationship with his daughter. The father, unable to control his disordered eros, corrupted the family structure as the daughter replaced his wife as a sexual partner.
From the physical to the psychological, incest takes many forms.
The modern view of incest moves beyond the physical to the psychological. The physical abuse can be replaced by a form of psychological abuse. Judith Warner cites Judith Lewis Herman on that issue.
Incest, she says, is “an abuse of patriarchal power,” a criminal perversion of fatherly control and influence. It is perpetrated, in many cases, by men who present themselves as the guardians of the moral order. And it isn’t always physical; in her 1981 book (with Lisa Hirschman), “Father-Daughter Incest,” she writes that the violation can be emotional, too, as when a “seductive father” oversteps his boundaries and goes places he never should in his daughter’s head. [Emphasis added]
When we consider the emotional or psychological incest, we see how the seductive father oversteps the normal boundaries between a father and a daughter. When a divorced father boasts about his daughter, in her presence, that she has a hot body and that if he was not her father, he would date her, he crosses the boundary. He gets into her head. The comment puts the daughter in an invidious position. The father erases the normal parental role as he indicates that she is now eligible to be a potential sexual partner. He gives her his highest approval. She wants to be approved but not in that way. She cannot correct her father for that risks his displeasure. The father forces the daughter to consider him as a potential sexual partner. She has to consider the idea if only to reject it. In that moment, the father publicly asserts his psychological power over his daughter. He reminds that her physical and sexual potential meet his approval. He asserts his sexual prowess, by his statement, and he abuses the psychological and emotional relationship. She is no longer his daughter; she is a viable sexual partner.
When the family is the microcosm of the state, incest has political consequences
If a father will inflict that emotional abuse on his daughter, what is he capable on a larger scale? Thankfully, most father-daughter incestuous relationships have no consequences beyond the family. Yet, the ancient Greeks viewed the family as a model for the state. Aristotle argued that the family was the building block of the city/polis. The Ancient Greeks understood that individual abuse, driven by a disordered eros, could scale to the city level if the father was able to gain control of the polis. The problem was the disordered eros that drove the father to the incestuous comments would have political consequences. On a larger scale, the disordered eros would have even greater consequences. What the seductive father does to his daughter within the family, the tyrant can do to a community within a nation. He will abuse it so that it will serve his disordered erotic political vision. He will seduce the state that he is supposed to protect and serve so that it is corrupted to serve his interests.
  Wohl, V. 2002. Love Among the Ruins: The Erotics of Democracy in Classical Athens, Princeton and London: Princeton University Press. p 221. Quoted in Larivee, Annie. Eros Tyrannos: Alcibiades as the Model of the Tyrant in Book IX of the Republic. The International Journal of the Platonic Tradition 6 (2012) p.9.
 Archibald, Elizabeth. Incest and the Medieval Imagination. Oxford, Claredon Press, 2003 p.190 https://books.google.co.uk/books?id=qfqWgZETHdQC&pg=PA190&lpg=PA190&dq=incest+tyranny+father+daughter&source=bl&ots=DLshrTQPei&sig=dTL85ACj75zw8i3gYG0TupLZN6k&hl=en&sa=X&ved=0ahUKEwiLlbiagKjPAhWMLsAKHTKIAKwQ6AEIHjAA#v=onepage&q=incest%20tyranny%20father%20daughter&f=false
 Warner, Judith. Pure Tyranny ,New York Times, The Opinion Pages, 13 June 2008
http://www.nytimes.com/2008/06/13/opinion/13iht-edwarner.1.13693546.html?_r=0 (accessed 24 September 2016)
Trump repeated his remarks on other occasions and has never retracted his views nor has he apologised publicly to his daughter.
 Aristotle. Politics. 1.1252a http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0058