As previously noted, the Supreme Court struck down legislation that discriminated between homo and hetero sexual orientation. The fact that adults wish to adopt children should not be impeded by sexual orientation. Certainly adoption of children is not a right, but a privilege, and as such can be granted and revoked. However, sexual orientation is not a criteria for determining whether or not adoption should be allowed.
The "rights" in this question only pertain to the child or children considered for adoption. What is in their best interest? If all criteria for adoption are satisfied, and the couple happens to be homosexual, will that in any way disadvantage the child(ren)?
As a general principle, adoption is a privilege that is created by statute in the states. There is no federal "right" to adopt children, although there certainly are certain familial rights of privacy.
If I were arguing your position, I would approach it as the other instructor advised as an issue of federalism. Second, I would be prepared to show authoritative studies or other empirical evidence that indicates homosexuals adopting children is detrimental to the welfare of the states. That, you would find quite difficult, as virtually all authoritative studies conclude exactly the opposite.
In addition, due to the breadth of your position, you will also run into legal difficulty in light of the U.S. Supreme Court's decision in Romer v. Evans (1996). In that case, the state of Colorado attempted to legislate significant restrictions on the activities of its citizens that were homosexual. The U.S. Supreme Court struck down that legislation, with Justice Kennedy writing: "Amendment 2 classifies homosexuals not to further a proper legislative end but to make them unequal to everyone else. This Colorado cannot do. A State cannot so deem a class of persons a stranger to its laws. Amendment 2 violates the Equal Protection Clause..."
It seems to me that your broad position brings you fairly close to the same type of position taken by Colorado.
The primary argument given in support of denying adoption rights to same sex couples is one that is rooted in religious belief systems. However, since we are, theoretically, a country which believes in the separation of church and state, this argument does not really stand up to scrutiny. The ONLY support that is in any way valid for this repressive legislation is the fact that the United States is a federalist system, meaning that it grants certain legislative powers to the states allowing them to make their own decisions. This is the same legislative power that allowed biracial marriages to be outlawed in certain states until the case of Lovung v Virginia declared such a ban constitutional. Some opponents of same sex adoption will attempt to use statistics that show children in same sex families are disadvantaged, but the problem with most of the comparative data is that the "researchers" in question are attempting to use data from single parent families as the comparison. Additionally, the bulk of the challenges faced by children raised in same sex homes comes from society, not from the family itself. They are discriminated against, persecuted, threatened, and otherwise taunted by a society that is frightened of anyone or anything that strays from what is perceived as the "norm" - in other words, there is really no "valid" argument (outside of personal religious beliefs, personal moral judgements, and the fact that states do have the right to legislate in any way they see fit until the federal courts find their legislation unconstitutional).
Therefore, if you are wanting to argue against same sex adoption in all 50 states, the best way that I can see for you to try and present your case would be to base it on the legal precedence that has accompanied federalism. You would have to argue that this is a decision that should be left in the hands of the individual states, and that some states, based on the demographics and belief systems that are most prominent, would be best served to maintain a ban. Perhaps you could argue that in certain areas open homosexuality is already so dangerous that there would be a danger posed toward the children of such unions that would be clear and present enough of a concern that it would override the civil rights of the gay family who wished to adopt and provide an otherwise loving home for the child.
excuse me, i am a homosexual and i would one day like to adopt a child. my mother adopted me and she was straight. i love children and i would raise them to know that there are other options for them. they would not have to think if i had a daughter oh if i bring my "boyfriend" home they will look bad at him. not its based on who they are. i find those who oppose adoption by the lesbians or gays repulsive in my eyes.