I think you'd also agree that the degree to which a relationship is consanguineous makes a huge difference too. For you you drew the line at first cousins, however they are very, very often capable of having unaffected children, but the risk skyrockets when we talk about siblings. Others may say that even second or third cousins marrying could also weaken the gene pool and should be banned. I just don't think you'll get a universally enforceable guideline here, as people are willing to tolerate different levels of risk and have different priorities. Basically the cultural factor is huge here.
Actually that's both true and untrue. Yes. For one person to have offspring with their first cousin, the genetical implications aren't "bad". However, we can't deny the fact that majority of people, if not almost all, who have children with their cousins, have done so more or less for generations and will continue to do so. It's not even a religious matter, but cultural. Then it's NOT minor/to no genetical implications anymore. Which actual studies and statistics have shown with no exception. So wouldn't it be nice if one could argue that hey, it's a cousin and not that bad. But then your parent were cousins, and grandparents. And your cousin's parents were cousins...
But whatever. I've met well educated people who know more about medicine than I do. But for some reason have this emotional attachment to the practice. And understandably, they were most often a result of this practice themselves, have children and loved one who were.