Board Thread:General Discussion/@comment-1918136-20140126051852/@comment-3060460-20140126055648

You do have a good point, and I can see where you're coming from. But Solid was raised to become the Perfect Soldier(not referring to Null/Gray Fox), to become a merciless killing machine, one that takes every order without question. One that could take Big Boss out. So he needed to be deprived of emotion so if a comrade died, he wouldn't care, he wouldn't let it get to him. Big Boss on the other hand, was raised in the military by The Boss, who although tried to break him out of his emotions, ultimately failed (case and point, Portable Ops and Peacewalker, as he showed constant emotion for his allies).

Solid is not a monster per say, he just lacks human emotion.