There is nothing about TitD that is Heavy Metal, things can be extreme, loud, fast and heavy but not be Heavy Metal. Converge isn't metal either, neither is shit like Pelican and other stuff along those lines, should Black Flag, Suicidal Tendencies (early not when they crossed over) and Husker Du be called metal as well? It has nothing to do with how good they are, they just simply don't play Heavy Metal. I don't care how a bunch of kids classify them anyways. Those same types would called Linkin Park and Disturbed metal as well.
The NYDM dudes are probably mostly in their 30's like me and probably suprisingly more tolerant of a band like TitD then I am since New York metal was always crossed with hardcore to some degree, especially when those dudes were coming up.
Besides, it is there site and I guess they can do whatever they want and if keeping out hardcore and nu metal means that much to them, ok.