When a person has capacity it means that they can absorb information and are able to make a decision whether you do or do not agree with them. It is within their ability to make a decision that is important and not just a decision that you would agree with.
This is the kind of person a leader would want as a participant, someone that can think for themselves and further whatever the cause might be in an intelligent thoughtful manner. The opposite would be a person that acts as though they are a zombie always agreeing just for the sake of agreeing and never thinking for themselves.
