I don't think Java Script is the problem. Java is. I have Java totally disabled and the only thing I ever have to enable it for are the tests here on BBR.
Selenia I love Debian Premium join:2006-09-22 Lanesboro, MA kudos:2
Javascript often is used to load such applets within a page and can also be used maliciously. Blocking both it and plugins unless you say yes is a good way to harden your browser against having vulnerabilities in the engine or plugins exploited, as is sandboxing.