Why did I get banned for no reason on minecraft?

Help! I was new to this minecraft server. Then the admin came over and said to me, "Hi there! We can see that you are new to this server. Would you like us to help you out?". Then I said to them "Okay sure." Then a minute later, they banned me for "having MCbans on record". What does this mean? Does this mean the admin was just pretending to be nice? Does this mean the admin was really being mean and abusive to new players like me?