, you won't be taken seriously if you can't come up with a source which claims the picture is anything other than what the BBC News article purports it to be. Just saying "the red cannot ANY WAY be from blood" is hardly a compelling argument and is clearly original research. Find me a reliable source which says "Image of Beit-Hanoun street with red water in it, definitely no blood" and I'll accept that the picture's provenance is in question, however the BBC and AFP are clearly reliable sources and what they claim is valid for inclusion in articles.
The only question over whether to include them is whether they satisfy the fair use rationale that they add information to the article. I'm undecided on this, but I'd hate to see valuable content not included because some people refuse to trust a clearly reputable news source.