It is common for politicians to be lampooned and the subject of satire. What is satire in the first place? Usually, appearances and positions are exaggerated, for the sake of levity.
What was different about the characterization of Michele and Brarack Obama was that they were depicted as armed and dangerous, terrorists that were not only complicit in terrorism but were somehow actually doing the terrorizing themselves. And why? Because they are black (and Sen. Obama's father was a Muslim). It's one thing to characterize Sen. Obama as a host of things, but you can't 'have fun' with someone being a terrorist these days after all the mess about Guantanamo, Iraq and domestic terrorism.
The Bush administration sanctioned former President Jimmy Carter for unilaterally meeting with Mid-East extremists to talk. Former President Carter was called all kinds of things, but no one characterized him as a terrorist. But Obama is black and his Dad was a Muslim -- so that's perfectly fine.
Terrorist = murderer. The guy is running for president. On what planet was this supposed to be either smart or witty? There aren't usually a lot of laughs when it comes to murderers, so I guess this was the New Yorker trying to be 'edgy.'