1.The first sentence "think of it as wrong or immoral". It should be "think of it as wrong or immorality"
2.The second paragraph "we cannot regard this kind of adultery as immoral". It should be "we cannot regard this kind of adultery as immorality"
First, you didn't have terrible grammar like me. It's great XDD
Second, although I didn't agree with your idea, this article is good and has a strong standpoint. Our basic physical needs is indeed important, and restrained by the moralities.
I think "immoral" is acceptable because "being" can be ignored.
And thank for your compliment anyway. :)
I agree that the open marriage is not immoral, but it's because couples themselves had reach agreements before they commit adultery. However, many cheated people do not reach an agreement with their spouses. They just want to pursue excitement. Would you still think that the adultery committed by that kind of people should not be called immoral? Just as you say, they are exceptions, so it's better for you tell readers that it's under specific situation.
And in your last paragraph, what do you mean for "hostility toward adultery is seen as a useful way to protect marriage." I think it's a little strange to say that "hostility" can protect marriage, because it's a kind of feeling. Maybe you can say "the crime of adultery can protect marriage" would be better.
So, that still means not every adultery is immoral!
Thank for your comments anyway :)