I.e., the doctor is not a callous man, it's just that he can't tolerate anybody!
This summation of Monygham's nature shows clearly that his cynicism is based
on a fundamental compassion. But it also sets out a grim dichotomy in which
"tolerance" can only be achieved by lacking that compassion
-- by being callous. "Tolerance," of course, is what is necessary
for people to live together in society, to be men "of the world";
in other words, a successful society is a callous one. Monygham rejects this
tolerance in favor of "passion" and "sensitiveness," which,
we recall, were attributes of Costaguana's most unsuccessful periods
-- see Decoud's exasperation that "We have political passions" ,
and the "great sensitiveness" of a certain sadistic officer.