I have found better alternative solution for the database exception bug than just IP banning.
I now start the wallet with "-maxconnection=10". That will limit connections that the wallet accepts so when all of those 10 connections are version 2.0.2, old version of wallets can't connect and that database exception doesn't happen.
You really should disconnect old incompatible versions after hard fork. Some people are lazy, some lack the needed skills to update their wallet
and some trolls just want to cause problems with old wallets. I saw few version 1.0.4 wallets connected to my wallet after hard fork.