Hi, Vampiric Touch got changed in 4.0.1 to fear the dispeller (With some talents) rather than deal flat out damage.
Anyways, to the exploit. The spell that fears you is a buff, and what that means is that you can use a /cancelaura Sin and Punishment macro to get rid of it instantly after dispelling.
In a code tag for you who can't spell (Or are just too lazy to!). ^_^
Code:/cancelaura Sin and Punishment