What's so bad about murmuring in your tent?  I guess that if we are going to murmur that would be the better place to do it. At least we wouldn't be murmuring in public in front of others. But it doesn't appear that God's too keen about us murmuring even in the privacy of our own homes. I wonder why?
 
Could it be that He knows that what you say at home is what you truly believe? We all can put on a show and throw the Christian jargon around in the company of others. But it's when you get home that the mask comes off and you speak your true convictions. God wants us to know that He who formed the ear is listening even in our living rooms. God is not eavesdropping in order to condemn us for saying something He doesn't like. His desire is that our faith would be real, real enough to take home!