There is no difference between a sign, a billboard, a commercial....Do all the signs you want litte damo boy.
Do you get to restrict what form of presentation you want to allow or disallow based on the "speech" you want to see?
Which part of the first are you not violating?
Either you say that people are not allowed to assemble (form a company) for the purpose of protest, or you say they are not allowed to petition through this specific means, or you say that they are not allowed to say what they want, or you are saying that they cannot assemble for any purpose and exercise rights....
In each of those you violate a portion of the first Amendment. Congress shall make no law...
It may seem scary to you that people can say what they believe, even if they are assembled as a corporation, but it is one of those things we allow so that we too can assemble and say what we want, and petition the government.