What could be more deadly than being unable to die?
Anything. Quite literally, anything at all. All of the things are more deadly than being unable to die.
Well... I am firmly in the pro-immortality camp. However, I have given thought to the quandary of the fact that for any given immortal being, the probability of becoming eternally trapped at any given moment in a "And I Must Scream" scenario is non-zero (though admittedly vanishingly small). An infinitessimally likely result will occur at least once in an infinite number of trials, however, so... that's a troublesome one.
Better to be immortal with the option of suicide, than to be literally incapable of dying.
via.
Sounds like sour grapes. I'd heard of people holding such sentiments; this is the first time I've actually seen them expressed myself.