Many people consider the recent movement to legalize same-sex marriage consider homosexuality to be something that is unavoidable for some people, and should be viewed as common and just as acceptable as heterosexual relations. All this comes from the idea that just because we have an inclination to do something then we must do it, and it is inevitable that we will do it.
I recently read the transcript of an interview regarding the LDS Church's stance on same-gender attraction and one quote I found particularly interesting was, "One of the great sophistries of our age, I think, is that merely because one has an inclination to do something, that therefore acting in accordance with that inclination is inevitable." (Elder Wickman)
The reason why same-sex marriage is even an issue is because normal heterosexual relations outside of marriage are already considered to be acceptable. If this first were not considered acceptable then the other would not even have been considered as a serious issue of consideration. Those who have attempted to affect and direct society first taught us that these things were normal and that we have urges that not only should we give into them, but that it is inevitable that we give in to our urges and desires. Once that idea had been established in our collective forma de ser (way of being) then the other question, that of homosexuality was raised. Given the forgone conclusion of the former idea, the latter conclusion seemed natural.
The only reason why some people think, "I don't see why that is a problem, it's not that different and in some ways better than what 'normal' people do." is because they are so deep inside the Greatest Lie and Sophistry of our time that they cannot see it clearly for what it is. These people may realize that if homosexual relations are truly wrong then all other sexual relations outside of marriage are also wrong, but because that idea was banished years ago from our society they see no problem with allowing the next logical step. They see it as a logical progression from allowing one thing, to allowing another and finally all things. Unfortunately there is an inevitable end to all of this and it is precisely this end they wish to ignore, for it was because of this natural conclusion that these things were not allowed in the first place.
They deny that allowing these things (not just homosexuality, but also relations outside of marriage) will lead to a fracturing of society and will destroy the foundation, or that which perpetuates, our society. But those who actively preach this doctrine do not wish to promote the consequences, they only want to promote the idea that these things are inevitable, or that there is only one natural way of progression, and this is it. Herein is the Great Lie of our time.