Different Worlds

I accidentally got in a bit of a discussion today regarding schools and guns.  The more I talk with non-gun people, the more I realize that we live in completely different worlds, with a completely differing set of immutable governing rules.  I think both of our worlds have gravity, but that might be all that we can agree on!  It really makes me wonder what we can do.  When someone's up is your down, how do you even find enough common ground to begin a discussion?