Not sure what kind of store this is but if I saw a sign like that in the door I would interpret the owners as being kind of kooky and would likely keep walking instead of going in to buy something.
Like if it were a coffee shop or diner, I'd move along to the next shop.
When I'm going for coffee, I don't want to be barraged with political opinions, I just want coffee.
At which point the owner would blame illegals or Obama for his business's failure. Definitely not blame the action of putting the sign....