Why guys steal other guys pictures?

We all know that most image thieves are women , but men who are known starting to do more than women. A guy who was talking to us sharing recent photos that I posted a photo that did not match their other . The guy looked musclar and mature when the other half looked like slim toned guy . He tried to convince me it was him until he confessed he took that picture on the internet . I said that's not cool or other identity stealing . But he believes he did nothing wrong he was not stealing a pic that only one was not her the rest was . I just wonder how it never really talking uu online , even when it comes to men . And I've had a few incidents like this happen just do not understand