Actually the answers to both questions are the same. There are exceptions but as a general rule moral crusaders have no sense of humour, especially if the joke is on them. Saving the world ... is a serious business... Making a joke of them can be more effective than a rational argument with all the facts on our side.
Secondly, these protectors of the ‘Rights of Man’ are likely to lose their limited cool and rip the the anti IAW posters down or vandalise them. Unfortunately at many venues destroying a poster is a much more serious crime than supporting genocide against the Jewish people. Still, if you catch them at it the administration may insist (in the interest of fairness) on all posters being removed. That really irritates the IAW crowd.
Lastly,when you post them right next to the originals, it can start off much needed discussion. The parody is close enough to fool the eye for a moment. Join right in. We love to receive photographs of the posters in position!"
Source: Five Minutes For Israel web site
Curator's note: Both of these posters are remixes of an original poster by Nidal El Khairy which may be viewed here