You don't. You leave them alone and they will leave you alone.
Unless you live in the land of freedom and colon cancer, most atheists are just regular people who don't need to prove anything. Occasionally you'll get the odd "Humanist" twat, but they are usually from religious backgrounds.
The reason these types of atheists are so prevalent in America is because it is a country inundated with Christianity,# and ideological patriotism. It's unsurprising that atheists feel they have to be so vocal in a country that combines religious ideology and government.
