Doesn't matter what the reasons are, they're not good enough. And as long as Japan censors porn I'll consider them to be even more afraid of nudity and sex than Americans.
"afraid of nudity" sounds ridiculous, even the prudish culture in north America doesn't mean they are "afraid" of it... I would say the word would be more "ashamed" of sexuality. As an example, the main crime for a politician to commit in the US is a sex scandal. Bill Clinton was facing impeachment procedures due to a blowjob. While the Bush administration could blatantly lie about WMDs and invade several countries under false pretenses with no legal consequences.
In my opinion that beats any type of pixelated dicks on JAVs for sexual repression.