It's generally not possible at a business-level to treat IE users as second-class citizens. So while your idea appeals to anyone who has ever done webapp development, it's not conducive to business interests.
After all, there's always another website looking to take the users that you're not willing to fully support.
But it's not about refusing to support them completely. Also, the difference between trying this strategy today and even 2 years ago is that CSS now has features that would be compelling to end users rather than just developers. Users couldn't care less if developers want to use Safari/FireFox/IE8 because they support display: table. But users are becoming more demanding in terms of user experience and as they realize that the alternative browsers let them have nicer typography and cool desktop-like animations/transitions they will begin to demand this kind of thing.
For a while, some die-hards will probably try to use Flash to mimic the experience that HTML5 and these new CSS features offer. But I think the uptake of Flash amongst new developers is less than that of standards-based practices. Simply by virtue of having more developers supporting the standards based approach, I think Flash will eventually be eclipsed until it is relegated to a niche, kind of like how Google Maps is everywhere now and MapQuest is dying.
There is this big assumption that users are resistant to change. I'm inclined to believe they're resistant to unnecessary change. We just need to make them feel compelled to change and users will do so. For the first time in a while, Safari and FireFox actually have compelling features to users that IE does not. That changes the landscape quite a bit.
So, when you argue with your client over this specification for hours, and they decide to give the job to someone who will make it consistent, then what?
From a business point of view, especially in the marketing world, you'll have a hard time compelling the every day firm to ditch IE support. And as I said in the previous thread about this same exact thing, the elites can do it and still get plenty of business, but is everyone in the position to be able to turn down a job because of this?
The answer is probably no.
EDIT:
I guess the real issue is more along the lines of an education issue, and people who don't grasp it, getting put in charge of whatever new micro-marketing site you're releasing this quarter.
Don't argue. Present your case as "You can have IE6 support or you can have features X, Y, and Z. Make the call." Sometimes they'll say they want IE6, and sometimes they'll want the features. But it should be framed as a tradeoff: you can't have both, and supporting obsolete browsers means you can't deliver functionality that may get you more users in the long run.
> But users are becoming more demanding in terms of user experience and as they realize that the alternative browsers let them have nicer typography and cool desktop-like animations/transitions they will begin to demand this kind of thing.
While many users may like these things, "demand" seems a bit strong.
And then there are the folks who don't like "cool desktop-line animations/transitions".
After all, there's always another website looking to take the users that you're not willing to fully support.