Attacking him in the dreamscape is not without its hazards. While it is indeed a risk that destroying Mechakara within his mind could have adverse effects on his psyche, it is far more important to note that if anything were to happen to your self within the dreamscape, you would be reduced to a vegetative state.

It would not be true death, I cannot trust that you would recover as Bertram or Gwendolyn did.

Dreamwalking in such hazardous conditions is not to be taken lightly. There is a reason I let this situation progress as far as it did.