The "Slippery Slope" argument used in gay marriage debate is invalid

I will do my best to make it interesting and vigorous. "Laying the playing field" First I'd like to say that I will not be making any moral judgements on the subject matter of this debate. I will approach the subject matter in a manner that neither purports to condemn nor condone as I do not see that taking a personal stand is germane to the debate. "Slippery slope argument" - (SSA) the position that acquiescence to a particular condition or activity is undesirable because it could possibly lead to a secondary condition or activity that is even more undesirable or a progression of conditions or activities of increasing undesirability; or that such an undesirable progression would be made more likely. My understanding of my opponent's position is this: There are those who oppose the government recognition and sanctioning of legal/religious unions or "marriage" of homosexual couples due to the fact that such recognition or sanctioning could/would increase the instance of aberrant/undesirable activities that are detrimental to society. Such possible aberrant/undesirable activities might include polygamy, incest, pedophilia and bestiality. My opponent believes that such concerns are unfounded and that "slippery slope" is an illogical argument. To win this debate I must show that those who might use the "slippery slope argument" (SSA) have a logical basis to do so. "The argument" First let's notice that the beginning condition of the SSA is "gay marriage" which involves homosexuality which is a sexual behavior. The conditions given as the possible progression conditions are all of a sexual nature: Polygamy - traditionally involves sexual relation between one man and multiple wives Incest - sex between family members other than between husband and wife Pedophilia - sex between an adult and a child Bestiality - sex between a human and an animal It must be noted that all of these sexual behaviours carry a stigma to one degree or another throughout recorded history and have generally been considered aberrant behaviour throughout the United States for the history of the country. Of course there are many examples in recorded history and the history of the U. S. where some of these sexual behaviours have sometimes been openly practiced or condoned but on the whole, especially within the U. S. , the general attitude toward these sexual behaviours has historically been that they are aberrant and detrimental to society. Nevertheless, attitudes of societies often change. They often ebb and flow with the changing values and philosophies of the times. Consider the change in attitude toward homosexuality in the U. S. Fifty years ago most homosexuals concealed their sexual behaviours for fear of reprisal. Today homosexuals hold annual parades in major cities in open celebration of their sexual orientation. Fifty years ago it would be exceedingly rare to see a homosexual on network television, either real or as portrayed by an actor. Today there are numerous television series devoted to presenting homosexuals, both real and as portrayed by actors. Fifty years ago one would be hard pressed to find an open homosexual holding a government office. Today we have openly homosexual members of congress and it is possible that an open homosexual may be appointed to the Supreme Court. As we can see, there has been a gradual change in attitude and acceptance of homosexuality in society in the U. S. But even today a segment of society still regards homosexuality as an aberrant behavior and one that is detrimental to society. That segment has arguably become smaller today than what it was fifty years ago. How would the attitude of society be affected if marriage between homosexuals were given official approval by the U. S. government? Would the attitude be more likely to become more favorable or less favorable? One must conclude that, by law, people would then be obliged to become more favorable toward homosexuality at least in outward action if not in personal belief. As mentioned, there is a segment that views homosexuality as aberrant sexual behavior. In the eyes of that segment, when one aberrant sexual behavior gains government approval and approval in society, does it make another aberrant sexual behavior more likely or less likely to gain approval in society? Let's ask it another way. If one behavior gains official approval by the government and society, does it make another, similar in nature, behavior more likely or less likely to gain approval in society? I say that it makes it more likely. And if it is more likely then those who hold the SSA against "gay marriage" have a logical basis to do so. I think I'll rest there for now.