I just wanna know if this is hacking(using auto-click) or some kind of glitch ....

I did say rejoin mods are alright since many players live in Asia where the internet is pretty terrible, which leaves them frustrated at having to reconnect all the time, but they can also be a very strong sign of a hacked client. However there really isn't any evidence of that (as opposed to a rejoin mod), however if they keep on being used in an abusive manner (or annoying as in this case, even if unintentionally) I might have to ban them. You might also have to consider that someone might have been trying to brute-force his account.