Essentially it's a shortening (or "contraction") of "he can't be forced/made to bleat" ... or in other words "this guy is so tough nothing ever will make him cry out in pain" ...
What does bleat mean slang?
: to talk complainingly or with a whine. : blather. transitive verb.
What does bleat goat mean?
to utter the cry of a sheep, goat, or calf or a sound resembling such a cry.
Is there a word bleat?
Noun. The characteristic cry of a sheep or a goat.
Whose sound is bleat?
The sound a lamb or calf makes is a bleat.