Microsoft doesnt have to defend themselves from such claims. Their proof is the fact that others can do it. Norton and McAfee made this claim that the technology was needed only to have it thrown in their face that it wasnt when BitDefender, AVG (Free version no less), Avast (Again free version) were able to over come such things and create a solution that didnt need what they called critical key items.
How can you boast that claim when it is proven that you dont need it? Microsoft didnt have to say anything more than go "See all of these companies, they work just fine with Vista without the items you claim to need". That alone is a bigger shot at them then anything Microsoft would say.
As for what they are thinking and why they wont change. I dont know. I used to think they were great. Till i opened my eyes. They are only big in the USA from what i know. They may have expanded a bit more overseas but they are still the landmark companies in the USA. Which is the only reason why they have such a following. They have a pretty box on a shelf at Walmart and that gets people thinking that their stuff is good.
But the truth is seen by my statements here and in just about every and any topic in the virus section. Anyone with real knowledge on the matter will tell you that these products are flawed. While they finally may have gotten their resource usage down. They are still as easy to get through for a hacker or virus writer like a hot knife in warm butter.
Will they change? Who knows. Should they change? Without a doubt.