They've spoken about it on a few occasions. And basically what they've stated is that they're trying to prevent trolls from screwing around on games. There's a big question in today's society about anonymity and social interaction on the Internet and how to prevent them doing what they do. It's a no brainer that being able to change your name at will will give trolls the ability to stay anonymous to the public regardless of whatever heinous bullshit they like to do. All I know is harassment on message and image boards is a big problem that's why many of them are starting to make it so you need to give some information about yourself (an email) out to make you not want to say disrespectful and hurtful things.
That's the worse excuse I have ever heard from Sony. Report the fuckers if they like to troll, it's not hard to do. It's not like they can make a new account to troll anyways.