No, it is not the case that claims about Muslims are automatically off-topic.
This is easily proven by the flurry of posts about islamic topics over the last three months. If anything, the needle is pointing too far the other way - Skeptics.SE is could be renamed "Questions about what Donald Trump tweeted and/or did someone say this about Islam?.SE" I am sure this is a temporarily fluctuation that will settle down soon, and we will be able to get our teeth into meatier topics.
I came late to this particular question, which had a lot of attention before I woke up. In its wake, I am left with a question of my own.
It is blatantly clear that the author of this book is religiously motivated, is making a ridiculous and unsubstantiated claim, is - at best - confusing correlation and causation, and the entire interview is based on a fictional Christian interlocutor acting as a strawman. (Socrates has a lot to answer for!)
But it is also clear, this question is going to be impossible to answer on Skeptics.SE, because we don't tolerate answers that simply dismiss the claim as freely as I have here, and there are no enormous, randomised, placebo-controlled studies empirically demonstrating the effect (or lack of it) of pork-consumption on wife-swapping.
So, my question is: What were you hoping that asking this question would achieve?
I am sure the question was asked in good faith. I have a lot of respect for your intelligence and rational thinking, as demonstrated in your answers. I am just confused by what your motivations were here.