Robert Geffner, president of the Institute on Violence, Abuse and Trauma at Alliant University in San Diego, said there is no such thing as consensual incest because of the "power differential" in the parent-child relationship.
"The issue goes back to informed consent and power," he said. "You cannot have informed consent if the power relationship is already in existence."
"If you are saying consenting adults can do whatever they want, then what about therapists and their clients, employers and their employees, clergy and their parishioners?" asked Geffner.
Those who have been in incestuous relationships with a parent -- even as adults -- "mix up" power, love, affection, attention and abuse, he said.
Like Phillips, they can lose their identity, struggle with forming meaningful attachments and can resort to drugs, self-cutting and even suicide.
Laws against moral crimes like incest and bigamy were enacted in the "hey day" of the anti-vice movement in the earlier part of the 20th century, according to legal expert Grossman.
"Like bigamy, you can't marry and trying to do so is a crime," said Grossman. "There was a criminal code in every state and a lot of them were enforced."
But laws against crimes like adultery, co-habitation and fornication lost favor, and by the 1950s and 1960s, even states where they were on the books, did not enforce them.
In 2003, the Supreme Court struck down sodomy laws in Lawrence v. Texas, ruling that states could not criminalize "private, consensual, sexual or intimate conduct that does not involve minors or coercion," according to Grossman.
Most of those laws then disappeared, except for bigamy and incest, because they had "implications for the institution of marriage."
States have defended legal challenges to consensual incest with several compelling arguments.
"The scientific argument is that the state has an interest to protect the future offspring of an incestuous relationship who might suffer disproportionate genetic risks," said Grossman.
Anthropologists Margaret Mead and Claude Levi-Strauss argued that the incest taboo was "among the essential mechanisms of human society."
"You have to worry about how it changes the nature of the parent-child relationship," said Grossman. "If it's not taboo, and you end up dating or marrying your own daughter, it may corrupt the way you raise your children."
If incest were not "absolutely off limits" in families, the natural affection -- sitting on laps and hugging and kissing -- would be compromised and unsafe, said Grossman.
"The state has an interest in protecting the welfare of children and the harmony of the family relationships," she said.
Families are also the "building blocks" of society, said Grossman. With incest, "you lose the possibility of a family connecting with another one and keeping society connected."
Meanwhile, Columbia's Epstein has taken an administrative leave, no longer teaching students, and preparing his defense.
As for the Swiss bill to lift the legal ban, it will not only have to pass Parliament, but a nationwide popular vote.
It will likely "take years to pass," if at all, according to Swiss journalist Urs Huber. "All the right wing, conservative parties have immediately protested against the idea."