Yet if I put a picture of a gerbil against a cloudy sky in the article on gerbils, nobody would say "clouds are irrelevant to gerbils" and take the picture out until someone removed the clouds from the picture. Relevance isn't enough; offensiveness matters.
It's not just relevance, it's prominence. The clouds wouldn't be prominent in the photo, they're just in the background. A person engaging in "gerbiling" would be very prominent. The fact that some people could be offended by it is irrelevant. A photo of a building with a small gerbil just visible in front of it wouldn't be acceptable either, because the building is too prominent and the gerbil isn't prominent enough, but it's certainly not offensive (unless someone's religion is anti-buildings, which wouldn't surprise me...)