While that might be true, you cannot simply log into their server and delete your stuff. There are, however, legal routes you can take to get the stuff removed.
IANAL but this isn't as clear as that. A contractor can't come in and take out the new bathroom he installed because you didn't pay him, and I'm guessing similar protections apply to repossessing a website.
Also, a reputation for destroying clients' web sites isn't going to help. You won't get far enough to explain "Yes, but…"