Which, to be fair, is a good point. It would certainly not be tolerated if a conservative (celebrity or otherwise--remember the rodeo clown?) mocked the president, and especially not if they fake killed him. The same should be true of the current president, but given the tepid condemnations of Snoop Dogg's assassination of a clown Donald Trump, I guess the precedent has been set.
The irony of the whole thing is that Griffin has nothing to fear about being sent to a federal prison for this "art" piece. The First Amendment exists, and this is protected speech. Disgusting, and she can still be mocked and derided and face consequences (work or social) for it, but she has no risk of being sent to prison over it.