I understand where you're coming from. For me it has to do with the overall message of the picture. Is the intent to mock Christ and make fun of Christianity (i.e. "Buddy Christ" in Kevin Smith's movie, Dogma.) or is it something like a picture of Jesus sitting, spending time with children, and he happens to be laughing? Jesus did have a sense of humor, his interaction when meeting Nathaniel in John 1:43-49 is proof of that. His response to Nathaniel wasn't so much Him saying to Nathaniel that there was no deceit in him despite his being an Israelite as it was a tongue-in-cheek response to Nathaniel's comment about Nazareth. It was, basically, Jesus joking with him. Nathaniel was actually asking, how do you know what I said when he asked how do you know me? Nathaniel also knew that Jesus wasn't close enough to the fig tree to hear Him, which gave Nathaniel the proof he needed.
Either way, it's ok to be mad about someone mocking us, our faith, our God and Lord and Savior. Just do not sin. Forgive them, ask Jesus to show the person the way.