1. Nothing disputed cosanguinity. For my money, it was the reason those other motivated explanations were missing
 
2. You link to HBD blogs who link to consanguinity advocates to dispute Lynn's data. So the idea there is no regulation and it is just trying to dehumanize Southern Italians is, imo, undermined.
 
3. Nobody serious advocates Padanianism. I usually see some curiosity about admixture from layfolk but oh well
 
4. Predictive Validity trumps arbitrarily bounded explanations. I say that because one can always focus on a set of events or factors in the span of time to say those contribute to what we see to the exception of biological factors. Same with deferring to ever more abstract cultural factors. It's just a narrative which cant be tested but makes sense to the creator since it fits in well with his other conjured notions about the world. Ultimately you cant produce the goods or predict as well as these other explanations, which can also predict the explanations you cite since they would help determine the behavior leading to them.