People have every right to pray, sing, speak, congregate, associate  from the mountain tops to the valley, from the roof tops to the basements, from City Hall to the Union Hall to speak their mind, criticize, condone, or condemn anything they want to.  They have every right to make religious references.    You, have every right not to listen.  In the future,  the Assembly should introduce the guest invited to give an invocation and then allow a moment or two for anyone to step outside for a moment until the invocation is complete if they choose not to participate for any reason.  No one should be pressured to "keep their mouth shut and stay out of political business".