Doesn’t matter. What happens when we let the government start picking and choosing which religions get to advertise? Especially for the next 3 1/2 years or so when we have a person in the White House clearly hostile to conservative Christian values? America is about freedom. If we have to get rid of that to fight them then we’ve already lost, we might manage to avoid becoming Islamic, but we won’t be America anymore.
Notice that no one said they cannot advertise. You extrapolated to that premise. We need, however, to stay informed of what they are doing. Also, if citizens are forced by proximity to view images or sentiments they disagree with on a billboard, they have recourse. I believe there is an individual who fights billboards with Christian messages. Religion on a billboard seems to be very controversial. It is an area in which we DO cherish freedom of choice, to the degree that we do not appreciate a harangue on the subject.
Having said that, this creates more of an alarm because islam is intextricably woven with 9/11 and hundreds of years of terrorism. They only wear “religion” as a disguise. This is the difference.
However, you are right that anyone with the money can advertise on a billboard. And it is also true that citizens have, with various degrees of success, protested controversial messages and images displayed. One thing that goes hand in hand with Liberty is Civility.
You're making a mistake characterizing Islam as simply a religion. It's a religion, a complete societal blueprint and system of government rolled into one.
Sharia law?. . .