This is the way I see it:
1. Some positive energy heals living creatures
2. Some positive energy can damage living creatures.
3. Therefore, all positive energy is not healing.
4. All positive energy damages undead.
I would think that those rules would apply for undead and negative energy, and the touch would be a negative energy that does not heal.
1. Some positive energy heals living creatures
2. Some positive energy can damage living creatures.
3. Therefore, all positive energy is not healing.
4. All positive energy damages undead.
I would think that those rules would apply for undead and negative energy, and the touch would be a negative energy that does not heal.