Re: Disable the voice dialer feature?
 

Go to Settings # Apps # Voice Dialer and select disable or force stop. This works for HTC EVO3D from Sprint.

Re: Disable the voice dialer feature?
 

I have an Android EVO 4g, this will disable Voice Dialer, not uninstall, this can be turned back on if needed. This service seems to be needed for Text to speech.

Go to All Apps -> Settings -> Apps-> select -> ALL Tab , which should show all the Apps installed, Scroll down and select -> Voice Dialer, This should open the APP, select Disable, I also cleared Data.
I am uncertain if one needs to Restart phone, Mine worked without restarting.
Plug head phones in and look at the Headphone Icon, no more mic on it.
This seems to have fixed the issue for me.