It requires one to abandon certain assumptions about human behavior. When you have discarded enough, many possible hypotheses that could explain the behavior appear:

  1. The person was misogynist, and actually believed that women
     are less capable than men, and their ideas less valuable.
  2. The person was insecure about their own position of power,
     and would seize upon any convenient excuse to undermine
     potential future challengers to his authority.
  3. The person minimized effort, and shot down the idea using
     arbitrary reasoning only as the means to avoid having to
     implement any part of it himself.
  4. The person was inexperienced and ignorant about socially
     acceptable behaviors, and was merely copying previously
     observed behaviors.
  5. The person was a troll, and chose that reason as the one which
     would be most inflammatory to the target.
  ...

I could continue, but it suffices to show that if something that actually happened cannot be explained while preserving your current set of assumptions, one or more of them must be flawed. In most cases, the easiest to strike down is the assumption that individual humans cannot hold logically incompatible beliefs, or cannot act rationally at some times and irrationally at others. Smart people can do some incredibly stupid things.

Another one that seems common is the assumption that all members of a synthetic tribe will tend to hold similar values and beliefs, and conduct themselves in a similar manner. People assume that members of a religion will behave in a particular way. People assume that members of a profession will act in a certain way.