Echo JS 0.11.0

I actually had plenty of experience with that type of clients, sadly. I've never gone back to IE6 fortunately, but I have with IE7, and that felt terribly outdated right back then.
Oh, sure, Microsoft was still releasing security patches. They could hide behind that. But now it doesn't, and keeping your software outdated, in the bliss of a false sense of security, is plain stupid.
The point is: stop working for them. You already know that you're not going to get anything good from such clients, and you'll find yourself regretting of not having asked for more money.