I wouldn't claim the ability to produce the most inappropriate such message; simply a highly inappropriate one in response to that question, immediately and reflexively, whether I wanted to or not.
It is, however, superior to your suggestion for a number of reasons:
1) It's considerably more achievable to spell out a three simple-word message with no punctuation in recognisable swastikas on an easter egg than it is to spell out a five complex-word message with punctuation in recognisable heroin needles in the same medium.
2) Swastikas are an immediately recognisable and highly historically, socially and politically charged symbol in a way that needles simply are not. You'd have a hard time even getting people to recognise a pointy blob piped onto a piece of confectionery as a hypodermic needle, let alone conveying the idea that it was for the purpose of injecting heroin.
3) "Fuck the police" is also an existing politicised statement, primarily associated with black gangsta rap group N.W.A., but also a broad anarchist sentiment taken in isolation, while "Your Child's Leukemia Is Hilarious!" is simply a highly distasteful fabricated statement without any precedent impact. It makes people go "ew", unless they actually have a child with leukemia, in which case it's just grievously cruel.
4) It's composed of radically opposed concepts, instead of randomly disjoint ones. Swastikas and gangsta rap lyrics emphatically do not belong together. More generally, anarchist and fascist statements aren't the most cosy of bedfellows. Heroin needles and leukemia hilarity are just randomly thrown together. Mine is subversive in structure, whereas yours is just surreal.
5) It's generally punchier. People can interpret the components immediately, and then their brains encounter resistance as they try to put them together. You get a sudden "WTF!?" moment since it's easy to read but hard to understand. With the heroin needle leukemia hilarity suggestion, the reader is presented with two quite hard-to-interpret elements, so the confusion happens at the wrong point. It's hard to read, but easy to understand, and the payload isn't worth the cost of delivery. It's like a shaggy dog story as opposed to a snappy one-liner.
6) When someone says "Your Child's Leukemia Is Hilarious!" they're clearly just going for the most shocking and distateful ideas that they can think of, since very few people think terminal childhood illness is genuinely funny. Once you realise that, you dismiss it as kind of childish. But people do use swastikas as symbols of their allegiance to horrific ideals, and people do say "fuck the police" and mean it, because they have legitimate and complex issues with authority figures and social institutions. Taken independently they could be serious statements. Only in combination do they become a jokingly obtuse, clearly over-the-top gesture of intentional offensiveness.
Back to the broader point, I believe people with the faculty I am claiming to possess would instantly and intuitively find mine more entertaining than yours, because they will likey favour inappropriate humour.
Hm. Very well then. I suppose I'm just an old curmudgeon who doesn't understand inappropriate humor. At least it's better than puns.
Partially to help reduce the typical mind fallacy and partially because I'm curious, I'm thinking about writing either an essay or a book with plenty of examples about ways by which human minds differ. From commonly known and ordinary, like differences in sexual orientation, to the rare and seemingly impossible, like motion blindness.
To do this, I need to start collecting examples. In what ways does your mind differ from what you think is the norm for most people?
I'm particularly interested in differences - small or large - that you didn't realize for a long time, automatically assuming that everyone was like you in that regard. It can even be something as trivial as always having conceptualized the passing of years as a visual timeline, and then finding out that not everyone does so. I'm also interested in links to blog posts where people talk about their own mental peculiarities, even if you didn't write them yourself. Also books and academic articles that you might think could be relevant.
Some of the content that I'm thinking about including are cultural differences in various things as recounted in the WEIRD article, differences in sexual and romantic orientation (such as mono/poly), differences in the ability to recover from setbacks, extroversion vs. introversion in terms of gaining/losing energy from social activity, differences in visualization ability, various cognitive differences ranging from autism to synesthesia to an inability to hear music in particular, differences in moral intuitions, differences in the way people think (visual vs. verbal vs. conceptual vs. something that I'm not aware of yet), differences in thinking styles (social/rational, reflectivity vs. impulsiveness) and various odd brain damage cases.
If you find this project interesting, consider spreading the link to this post or resharing my Google Plus update about it. Also, if you don't want to reply in public, feel free to send me a private message.