One of the curious things about pleasure and pain is the way they've been manipulated by evolutionary processes. A parent might find themselves prepared to run any hazard to protect their offspring; this is so, not because they have ruminated on their duty in such a case, but because the agony of their child is more nearly felt than the agony of their own soul. I don't have children myself, and I won't claim moral and physical courage where I haven't been tried. But I will believe that the anguish of losing a child eclipses in full measure again the pain of dying oneself.
Now, it often happens when a person rises to the occasion in some heroic way, that they express a becoming modesty: "Any man would have done the same." But what this really means is, "Any [healthy] man would have felt the same".
And that's why the doomsayers are wrong about the pleasure-principle as a societal foundation. Because Nature furnishes the norm, and Nature selects for group preservation.
-josh