Normally if VirusScan Access Protection is NOT set to "Prevent McAfee services from being stopped" you should be able to stop McShield anytime from Services applet. Otherwise only setting the startup mode to disable, and rebooting the computer, might work. (Killing the process itself could also be controlled by Access Protection)
Please open the VirusScan console on the host in question and disable Access Protection momentarily and try stopping McShield (try also stopping McAfee Framework Service, because this will start McShield again; or when you stop Mcshield, put it in Disable startup type.)
As for the Validation Trust Protection service: the dependency could be because of what is described in KB60356 (see Summary section).
Services are greyed out unless you go into the registry and remove the dependencies regardless of access protection. mcshield depends on mfevtp, mfevtp depends on mfehidk. If you remove the depencies and set the mfevtp start type to disabled(dword value =4) then reboot the machine will take ages to startup.
The notion that our services will never interfere with anything nor required to be stopped is beyond aggrivating. and what are we at, 5 services now?!?!