Blacklisting specific tags from an input format instead of whitelisting
You can get that functionality out of the box with the HTML Purifier module.

Once you've installed the module, go to the admin/config/content/formats page, choose the text format you want to edit, and select the "HTMLPurifier" checkbox. In the settings below, quite a bit further down the page, you'll find the ForbiddenElements textarea:



That's where you need to put your disallowed tags. It's probably worth looking at the rest of the settings to make sure they match up with your expectations (there are a lot of them though, HTMLPurifier is pretty configurable).