Final answer:
The Natural Law Theory is most often used to support the view that all homosexual acts are immoral. According to this theory, homosexuality goes against the purpose of sexual acts, which is to produce offspring. Atheistic Natural Law Theory suggests that if same-sex interactions exist in nature, then homosexual acts among humans would be morally good.
Step-by-step explanation:
The moral theory most often used to support the view that all homosexual acts are immoral, even if between consenting adults, is the Natural Law Theory. According to this theory, the morality of homosexual acts is determined by whether they are in accordance with natural laws. The Natural Law Theory argues that since homosexuality does not lead to procreation, it goes against the purpose of sexual acts, which is to produce offspring.
Atheistic Natural Law Theory, a variant of the Natural Law Theory, argues that if there are instances of same-sex interactions in nature that produce physical pleasure, then homosexual acts among humans would be morally good. This theory suggests that the purpose of orgasms is not solely for reproduction, but also to experience pleasure.
It is important to note that these theories are just one perspective and do not represent the views of everyone. There are other moral theories and viewpoints that support the moral acceptability of homosexuality.