Such a moral foundation opens the doors to virtually anything . . . over time. It is illogical to say moral upheavals like bestiality will be normalized shortly after the broad adoption of homosexuality. Relativism oftentimes takes time. Only with a constant onslaught of academic elites lecturing the people about how small they are to hold a certain ethic; TV comedies, reality TV, and movies constantly portraying such a lifestyle as free, open, funny, and "just like everyone else;" a theological reassessment of what God really things about the subject; a re-eduction of the young through government schools; and an increasing boldness upon those who live in a questionable lifestyle will morality be changed. This, obviously, takes time.
This is exactly the sort of pattern that the fight for homosexuality took. It began with an academic elite lecturing us about how stupid and empty headed we "little people" really are. And then, slowly over time, more and more producers and actors began to include and promote the homosexual lifestyle as something that is funny (but not in a demeaning way, but rather as something that can be enjoyed), non-freakish (getting the audience to say, "hey, he/she is not different than me"), and getting the audience to truly enjoy and respect homosexuality.
At the same time, many in the theological community began to question what the Bible and other religious texts said about the subject. Theological liberals, in particular, began to question the Bible's inerrancy saying that it is an ancient document and thus irrelevant for our times. Others accused its writers, like the Apostle Paul, as being unaware of things like sexual orientation and thus unqualified to speak for God authoritatively on the subject. Many simply ignored the texts and moved on. Others argued that the Bible condemned heterosexuals practicing homosexuality because it goes against their nature. This implies that the Bible favors homosexuality so long as the homosexual was born with such a sexual bent.
Another important advocate in the social evolution of morality is the public school system. Public schools are oftentimes the forefront of cultural wars. The government oftentimes pushes an agenda that many parents are not in favor of. Then come court cases, legislation, elections, school board rulings, hearings, newspaper articles, academia weighs in, etc. All along nothing in the school system actually changes. Public school is the only institution where parents do not have much of a choice on what their child is taught by strangers, thus robbing parents of their primary responsibility of educating and training their child. Public education allows indoctrination oftentimes without the parents even knowing about it.
Finally, there was the "coming out of the closet" movement that continues to this day. Increasingly, it is becoming more and more common for people to openly admit and parade their sexuality. This reveals that society is more open to the idea and have gone beyond the "yuck factor." Thus, seeing two men or two women hold hands at the mall is not as gross as it used to be. Eventually, society gets used to and eventually asks, "what's the big deal? Its their business."
This is the pattern of how morality gets changed in a society whose moral foundation is relativism. Relativism is the branch of Darwinian evolution and secularism. If life itself and everything that surrounds us is nothing more than an accident, then is there really such a thing as right and wrong? Naturalism implies moral relativism
Take this pattern and the shaky worldview in which it is based on and one can easily see how our society, over time, will embrace almost anything. If there is no such thing as objective and universal morals, then anything is permitted once people get used to it. This opens the door to anything being permitted and embraced.