The difference here is that you could sell a program that could cause a phone self-destruct (for instance, damaging the /Windows folder which will cause the phone to fail to boot) and require a manual reflash (which while is not a difficult process, would still probably require most users to bring the phone to a store to do it).
Since in all cases, Microsoft can only examine binaries, and can't see if such a Trojan horse exists, and even if they could see the source, it is still possible to obscure the behavior. If such a self-destruct feature is found, Microsoft can remotely delete the application, the Android Marketplace has the same sorta kill switch for the same reason.
If the program is just delisted, Microsoft won't remotely delete it (at least according to their press release). If you believe them is an entirely different problem.