Where's the options page?
This plugin is quite simple, and therefore doesn't need any configurable options. Just upload the plugin, activate, and rest easy knowing that IE6 is officially banned from your site.
What do you mean "It will crash their browser"?
The "No Thanks" button is a link to CrashIE {don't click that link if you're using IE6}. CrashIE uses a well known bug in IE to their advantage and exploits it with no mercy. The bug is simple, and it's not a "critical" crash. It will simply show the user the ever famous "Internet Explorer has encountered a problem and needs to close" message. After that, they'll have to close the browser and start all over.