Gay marriage should be legal

I will recycle a few arguments from my last debate on this subject, since none were addressed in that debate.Contention 1: It harms nobody, and infringes on nobody's rights.This one is fairly self-explanatory. Gay marriage does not harm anybody. That's it. If you don't like it, then that's fine, don't get one, but it doesn't cause direct harm towards you if others do so. It is a private act between consenting adults - this counters the exceedingly common argument that marriage will be redefined to include bestiality and other things (since animals can't give consent), which would cause a 'moral breakdown' of society. Polygamy is another possibility raised by critics of gay marriage as a possible thing that can happen in the future, which actually is slightly more valid (since it is also between consenting adultsContention 2: Legalizing gay marriage only affects how the federal government recognizes marriage It is often said by opponents of gay marriage that by legalizing gay marriage, we are forcing everybody to accept its existence. This is not true. Churches would not be forced to perform gay marriages, and same-sex couples could simply get a marriage license. Only the federal government would be 'required' to accept gay marriages, and only to the extent to provide the same government benefits (such as filing jointly on taxes) as traditional marriages.Contention 3: Allowing same-sex couples to enter into committed, monogamous relationships would reduce the spread of STDs among gays.This is an argument that I hear, strangely enough, used against gay marriage. However, in monogamous relationships, there is no chance of STDs spreading if neither person has one. If gay marriages were legalized, more people would want to be married, thus reducing the spread of common STDs.Contention 4: Same-sex couples can adopt children, and raise them just as well as any other couple.I'll cite this PubMed article for this: http://www.ncbi.nlm.nih.gov...Children raised by same-sex couples progress from school just as fine as children from a heterosexual couple. Now, I am aware of there being studies that reach the opposite conclusion, and I acknowledge this. However, these studies often make flawed comparisons. They seem to ignore many factors. One of these factors would be the fact that same-sex couples get their children from orphanages and shelters (since it is biologically impossible for them to have children of their own), which likely accounts for any claims that children from same-sex parents are more likely to have been victims of abuse. If a similar study were conducted on the ability of infertile couples to raise a child under the same conditions as these flawed studies, I'd expect the results to be similar. Furthermore, as my linked article states, children from any family type are more likely to do well in school than children who live in orphanages. This would mean that in order to prove same-sex parenting is bad, you would additionally have to prove that the children would be better off in an orphanage.Another factor is discrimination against same-sex couples. This would be present in any study outside of a country that is overall more accepting of same-sex marriage. This is also one case where same-sex marriage would help. While this wouldn't immediately change everyone's opinion, people would, over time, become more accepting of same-sex couples, and they would face less discrimination.In order to counter this argument, I expect a credible study that is free of fallacious logic and which makes conditions as similar as possible for the same-sex couple and the traditional couple (as well as their child). This is simply the scientific method - only one variable can be changed, and all other variables must be as similar as possible. It would also be nice to not have the study funded by any activism group against gay marriage (e.g. AFA, NOM, etc.), to ensure that there isn't any conflict of interest.I feel that this is enough for the first round. I await my opponent's arguments.