Choosing to write web applications for one platform is not equivalent to choosing to write desktop applications for two reasons:
Firstly, you're ignoring the history of the Internet (the whole reason it existing, if you like). It is designed for allowing everyone to interconnect. That is why the standards were created - so that anyone with software that complies with the standard will work. That is why the Internet has been so successful so quickly (it would have happened regardless of whether Microsoft had created IE or not).
So, to hijack the work that everyone has done for the last 30 years for the benefit of one particular group (purely because you apparently cannot be bothered to learn how to write a website properly), is either selfish or stupid. So, on that first count, yes, you are an idiot - don't use tools unless you know how they are supposed to work
(As an aside, because the web development/debug support that IE has is so much poorer than Firefox, you're making life much harder for yourself too.)
Secondly, you're failing yourself as a consumer. The only thing that keeps innovation and progress going is competition. Writing a website that only works with IE denies browser competition, and so ensures that little or no progress will be made by IE. So, it is your fault that IE has almost no development over the last few years!
Given that IE already fails to follow Internet standards when talking to Microsoft's IIS server, it seems very likely that the version of IE built into Longhorn will have a raft of extra consumer features (probably integration of existing products into IE) that use proprietary protocol that ONLY WORK with IIS! If that does happen then your choice as a consumer will be reduced yet again!
So, on balance, I have to agree with the guy who called you an idiot - you are not only working to undo 30 years of work on the Internet, you are working to reduce your own choice as a consumer, and deny that choice to other people.
/david