There are two main ways that we can make this argument.
First, we can argue that the Court should have upheld the Texas law. We can say that governments have the right to enact laws to uphold moral standards. In this argument, we can say that a government has the right to prevent people from doing things that most other people think are immoral. For example, the government has the right to prohibit bigamy even though that is private conduct and there is no clear victim of this crime. If the government can do that, it can also prohibit homosexual conduct.
Second, we can take the opposite view and argue that the Court made the right decision but did so for the wrong reason. Here, we can say that the Court should have struck down the law on equal protection grounds. It should have said that laws cannot treat homosexuals one way and heterosexuals another. This would have raised sexual preference to a protected status and would have been a much more sweeping way to promote the rights of gay people.
Thus, we can disagree with the Court’s decision for two rather opposite reasons.