I looked into this a little bit for my own personal curiosity. You are right that AIG does not teach this, though they acknowledge it as a view some creationists hold. Their reason for rejecting it is because hypothetically a cloned human created from two females would have to have a sin nature. I love AIG arguments.
However, the idea that a sin nature is passed on biologically through the father is found all over in popular level Christian theology explanations, as a quick google search will show. So the idea that McKnight just concocted a straw man and intentionally misrepresented creationist beliefs to make something he disagreed with look bad doesn’t hold water.
An apologetics ministry here: [quote] Some Bible commentators, with whom I agree, hold the position that the sin nature is passed down through the father. Support for this position is found in the fact that sin entered the world through Adam, not Eve. Remember, Eve was the one who sinned first. However, sin did not enter the world through her. It entered through Adam. Rom. 5:12 says, “Therefore, just as through one man sin entered into the world, and death through sin, and so death spread to all men, because all sinned.” The concept behind this is called Federal Headship. This means that a person (a father) represents his descendants. We see this concept taught in Heb. 7:9-10, “And, so to speak, through Abraham even Levi, who received tithes, paid tithes, 10 for he was still in the loins of his father when Melchizedek met him.” We see in Hebrews that Levi, a distant descendant of Abraham, is said to have paid tithes to Melchizedek when Abraham was the one offering the tithes, not Levi. What this means is that there is biblical support for the idea that the sin nature was passed down through the father. Since Jesus had no literal, biological father, the sin nature was not passed down to Him. However, since He had a human mother, he was fully human but without original sin. [/quote]
GotQuestions [quote] Because of Adam and Eve’s disobedience, sin has been an “inheritance” for all of their descendants. Romans 5:12 tells us that, through Adam, sin entered the world and so death was passed on to all men because all have sinned. This passed-on sin is known as inherited sin. Just as we inherit physical characteristics from our parents, we inherit our sinful nature from Adam. Adam and Eve were made in the image and likeness of God (Genesis 1:26-27; 9:6). However, we are also in the image and likeness of Adam (Genesis 5:3). When Adam fell into sin, the result was every one of his descendants also being “infected” with sin. David lamented this fact in one of his Psalms: “Surely I was sinful at birth, sinful from the time my mother conceived me” (Psalm 51:5). This does not mean that his mother bore him illegitimately; rather, his mother had inherited a sin nature from her parents, and they from their parents, and so on. David inherited sin from his parents, just as we all do. Even if we live the best life possible, we are still sinners as a result of inherited sin. [/quote]
Genesis and Genetics [quote]The Bible talks about our “sinful nature,” “the flesh,” and “carnal man” all of which refer to an attribute found in all humans: a propensity to sin. So the question is: Is this propensity to sin in our DNA? The answer is yes, sin nature is hardwired in us and in our DNA. We are not forced to sin, but we have the tendency to sin. This is not a God given tendency, but rather a result of Adam eating the forbidden fruit in the Garden of Eden some 6000 years ago.[/quote]
[quote]We have only recently discovered that the epigenome can change in response to diet, stress, nutrition and the environment… and that these changes occur throughout an individual’s lifetime. Also, the epigenetic changes that come about by the choices we make, or the situations we find ourselves in, during our lifetime, can be biologically passed to not only our children, but can reverberate far into the future affecting future generations. So, why would it be so hard to believe that Paul was right on target when he implied, in Romans 5, that something happened to all humanity because of Adam’s sin.
So why would it be too much to believe that significant changes took place in their epigenome, which was then transferred to future generations.The Bible teaches, even though Eve was the first to sin, it was through Adam that sin entered the world.
"Wherefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men, for that all have sinned. [Romans: 5:12]
Certainly, mentioning Adam specifically could be no more than laying blame at his door since he was the head of the human race to whom the original warning was given. On the other hand, questions have also risen as to how much epigenetic change is transmitted through the sperm of the male… One paper concludes that “sex-specific, male-line transgenerational responses exist in humans”.  While other studies suggest that RNA found in human sperm might also affect human inheritance. [/quote]