Disclaimer for the humorless, braindead liberal (but, I repeat myself!):
This is a work of satire. The fact that the fictional character satirized on this poster is carrying a gun, does not mean in any way that we wish any harm to befall President Obama because he is half black, or half white, or half baked. "Get off my lawn" is generally percieved as a "code word" for..."get off my lawn".
If you wish to infer that I, or the character portrayed on this poster, might be less than perfectly satisfied with the current administration, you would not be far from the truth.