Why does it seem that Atheist can't mind their business?

I'm from San Diego, and there has been this big debate to get rid of the cross at Mount Soledad(for decades)...all because of one person who happened to be an Athiest....why do they let it bother them? Why can't they just let it be? Same thing with Christmas on the Prado...an event in Balboa park that celebrates the birth of Jesus Christ. A group of Athiest complained and the event was changed to "December Nights". Christmas will always be known as a Christian feast commemorating the birth of Jesus.