What a story! So he even knew you personally, but that didn't stop him from stealing your phone and then giving it to his girlfriend? Amazing!
I think you're pretty right: these type of people never change. If they develop a criminal instinct, they'll never be able to get rid of it.
Technically the acount from @sami100 could be deleted from the blockchain through one of the next hardforks. Yet, as far as I know it's a political decision to not block any accounts since this would affect the dezentralized character of the platform. Until a certain degree I second that perspective, however in this case we're talking about a criminal that doesn't do anything on this blockchain than ripping off other users. So he's not even a contribution to the community, he's pain in the ass.
I guess the decentralized philosophy is great, unless it opens doors for abuse. We need tools to handle such situations and people. Just sitting and watching doesn't seem very contemporary to me.
He was my classmate! Studied 9 years in the same classroom!!! I think it should be voting or something to ban someone. On the other hand nothing will stop that guy from making a new account and start stealing again!
OMG - then it's even worse!
I have no idea if banning would be a possible solution. I just did a video about exactly that question - and some of the first answers given in the comments are really interesting. It's a tricky thing: On one hand you want decentralization / open doors / no barriers. But on the other hand you don't want to hang with assholes..