Not to mention that this could get you in some legal hot water depending on where you live.
What if you want to iterate over the return value of document.open? It's perfectly legal ECMAScript.
If I write a program that randomly crashes when I type in the URL of your website, should you be liable for that? Of course not. Any crash is Microsoft's fault, not the web developer's.
1) Intent matters. Clients won't go to your site.
2) It is MS' fault. No amount of JS should ever crash the browser, at worst it should replace the page with "sorry this page has crashed, please continue browsing elsewhere" like what chrome does.