Becoming vocal, whether by yelling out, screaming, or even vocally begging has also been categorized as a failure to remain stoic in the face of punishment or torture. Yet very effective tortures do succeed in making these things happen. Psychological tortures, or ones involving sleep deprivation, isolation, or long-term suffering are more apt to break people and could result in all sorts of reactions, perhaps even crying, but more like mental collapse crying rather than crying from pain. Crying in men is not as easy as just applying more pain and the notion assuming this is the case just seems fanciful.
AltanativeFTW:
Even big, tough, muscular guys would become traumatised and cry when receiving the kiss of leather from a cat o'nine tails or a Canadian prison strap.
So, I'm wondering where you are getting your evidence for this claim? I'm also curious if you yourself are easily brought to tears from the pain of a spanking? I know I'm not, and I still haven't 'cried' for other, more intense pains from injuries or whatever. I don't even cry at funerals. (And again I believe this is the conditioning of what is expected for how a man should act. ) And yet, like someone else mentioned, I can cry from a movie, book, or song.