Refraining From Inquisitiveness
The spying/inquisitiveness from which we are stopped is one which is ill-intended. At times, this arises from jealousy and at times from extreme malice and animosity. Both these things are totally contrary to the relationship of mutual sympathy and brotherhood which believers must maintain. As far as the matter of finding out the circumstances of some brother is concerned in order to help him or if at the state level arrangement is made to remain aware of the circmustances of people so that it can fulfill the responsibility imposed on it of maintaing law and order and taking care of its citizens , these do not relate to this prohibition in the slightest way. What you are referrring to in your example is not spying or inquisitiveness in that sense, since someone is openly discussing a political matter which in itself is a topic open to public discussion and you happen to hear it. Had it been something personal instead then it would be better to leave that place.