Case Study
Snopes.com is one of the most respected general-purpose fact-checking sites. It has investigated this viral e-mail claim and cannot rule it false because it cannot find any other use of this or a similar photograph on the web. Snopes is very careful to not label something false without very good evidence. It clearly was not taken in Phoenix as is claimed by these stories, but rather Los Angeles judging from the background. This would make the sign's reference to Arizona very suspicious. However, it has not been proven to be a false photo.
There are essentially three possibilities:
1: It was photoshopped. Many times people change the text on signs. If this indeed happened, the photoshop edit was very good.
2: The protester was a plant. An anti-immigration activist could have joined the protest and displayed the sign long enough for his collaborator to photograph it. There are other known cases where it is likely (although not 100% proven) that someone infiltrated a rally to discredit its participants. For example, see reports on claims that a Clinton supporter raised a placard that said "Rape Melania":
https://www.buzzfeed.com/josephbernstein/inside-the-alt-rights-campaign-to-smear-trump-protesters-as?utm_term=.kbPvgA5Xd#.sgQ0rByoe (note: Buzzfeed sometimes releases reports early without sufficient checking, as is evidenced by its release of the alleged "Russian Dossier" on Trump) or
http://www.9news.com.au/world/2016/11/17/14/58/rape-melania-sign-confirmed-real-but-who-really-cares
3: It is real. This is the least likely possibility for many reasons. Besides from the obviously naive and goofy demand, it is inciteful to police, who almost certainly would have taken away the sign at a minimum. After all, it is a "terroristic threat" and is almost certainly not protected free speech. In fact, other protesters, many of whom were carrying American flags, would have probably demanded it taken down.
Nevertheless, it is possible--but very hard to imagine--that someone would actually carry such a sign, and it has not been proven false.
In doing some initial research into this photo (e.g. by searching for it through Google images) one will find an abundance of very hateful and provocative webpages condemning this protester and immigrants in general (even though we don't even know he is an immigrant). Much of it is racist and concludes with what the US should do about immigration and our welfare system, not to mention the 2016 presidential election.
Do some searching... What can you find about it? Can you get to the bottom of it?
