I just don't believe Nico is malicious and he dislikes Schumacher for those very tactics.
Proving a point? Hamilton is super aggressive overtaking and defending. Without hearing the tone that's what Nico could have meant "why should I back out because he cuts me up". Right or wrong (probo wrong) Hamilton has been a little cutting (pun intended) previously so perhaps, just perhaps Rosberg meant 'why should I always yield'. I think he was wrong here, marginally, but that's far from the monster crash creator being created. He is clever and would never, intentional or not (and I doubt intent) admit intent.
Rosberg has been squeaky clean his whole career and this vitriol I'm afraid is more to do with who he is team mates with.
If it was Hamilton in the same situation how would it be judged? I know where I was Hamilton/Webber Singapore.