Yeah but... Where are such billboards allowed in Saudi Arabia, for instance? Probably no where. It's a matter of creeping islamism: First it's offensive to the "congregation" (what a joke to refer to a bunch of these cutthroats as a congregation!) if the billboard is near a mosque. Then it's offensive if it's within eyesight of any muslim. Then it's offensive if it's anywhere in the country -- even if muslims can't see it. Then it's offensive if an infidel walks on muslim ground with his filthy feet.
Some of us would probably object to a mosque being called a house of worship. Islam comes much nearer to being an analog of the international communist movement.