"Photoshopping" or media manipulation is easy and convincing. What protestor's signs are saying can be replaced, so can T-shirt designs. Put a person in a photo at a party who was never there. Paste a controversial figures face over an innocent person a president is shaking hands with. And of course the easiest of all: slap a caption on a photo that is completely false or out of context.
Taking that image and doing a simple "reverse image search" can quickly tell you the truth behind the image.