I agree that a partially armored vehicle, if struck in an unarmored facing by Small Arms fire (even if only the turret is unarmored), can be destroyed by that fire. This is definitively answered in A9.51:
A9.51 vs VEHICLE: Spraying Fire (like all forms of Area Fire) has no effect vs an AFV, but can affect Vulnerable PRC and unarmored/partially armored vehicles in the same manner as Small Arms Fire.
A related question, though, is whether a partially armored vehicle, if in a Location attacked by the Infantry Target Type, can be destroyed, even if presenting an unarmored facing toward the fire.
C3.32 INFANTRY TARGET TYPE: The Infantry Target Type can be selected only when firing HE [EXC: AP or HEAT vs an unarmored target (8.31, 11.52)] and only against an unarmored target. All AFV (but not their Vulnerable PRC) in the target Location are immune to damage from a hit on this table, other than that resulting from damage to terrain (B24.121). All other in-LOS enemy units in that Location can be hit [EXC: those immune as per 3.4], and all that are hit are then attacked on the IFT with a single Effects DR; see 3.4.
C3.41 The Infantry, as well as the Area, Target Type may be used to attack a[n] unarmored-target/unmanned-Gun/building/bridge/vehicle, and may also attack a hex devoid of such. [EXC: The Infantry Target Type (3.32) attacks a specific Location rather than an entire hex, and cannot be used to attack an AFV.]
I believe the answer here is no.
My reality argument is that Small Arms fire is directional: the bullets are streaming in from one direction. With HE + ITT, though, the HE rounds are landing in the Location and scattering fragments in all directions from the point of impact, so even if the partially armored vehicle is presenting an unarmored facing toward the firer, when the HE rounds hit, the fragments may be impinging on a different facing of the vehicle. Vulnerable PRC, though, are still in jeopardy if the vehicle is hit.
