Neopets cannot keep people from misusing the Internet. You should have anti-virus to begin with. If more people would take responsibility for their own behavior on the Web, fewer viruses would be spread around.
The reason they take away accounts that are hacked is precisely to keep people from misusing the site. You complain about misuse, but you also complain about them trying to stop it. What, exactly, do you want them to do?
As for passwords, using weak passwords is something that people need to stop doing. Do not use words from any language. Do not use your birthday. Do not use your pets' names. Learn how to create complex passwords, and you'll have fewer problems. Again, people need to take responsibility for knowing how to protect themselves online.