I know this is a joke, but wrong about what, exactly? I don't get it.
Also, and maybe this has something to do with the joke I'm not getting, the way complex numbers are motivated in school is a lie, and a stupid one. Mathematicians were perfectly comfortable with certain equations having no solutions; the problem was when their equations told them there were no solutions when they could see the solutions: the curve x3 - 15x + 4 crosses the x-axis, but Cardano's cubic formula gives up due to negative square roots. Imaginary numbers were originally no more than an ephemeral reasoning tool, and were only reluctantly accepted as entities in their own right because of how damn useful they were.
The numbers are imaginary, thus theyte not real, thus the math magicians (not gonna undo autocorrect there) are wrong and refuse to admit it because they insist imaginary numbers are real
Don't apply actual knowledge of what imaginary numbers are for this exercise
Ok, so this is a "joke" which is only funny to people who do not understand the context, and moreover jump to insane, unsubstantiated conclusions rather than expending an infinitesimal measure of effort to understand something they haven't seen before. It's active mockery of the very concept of being open to new ideas.
No, the joke plays on the two meanings of "imaginary" - one being "made up, not real", and the other being the mathematical construct. The fact that you don't get it doesn't make it mockery, it just means you don't get it.
I might not find a joke funny, or I might not have the necessary context to appreciate it; that's "not getting" a joke. If it's possible to have too much context to appreciate a "joke", it's at the expense of people who know more than the audience.
It might seem harmless, but the purpose of a joke is to draw a distinction between those who get it and those who don't, fostering a sense of community. In this "joke", the in-group is people who don't know something; the community ideal fostered there is that knowledge is undesirable, that anything that seems unintuitive to the uninformed mind is inherently ridiculous. The "joke" has no effect if it doesn't do this. Entertaining the idea without challenge is dangerous.
That's where you're wrong. The joke is based around a play on words: the generally accepted definition of imaginary, and a math term. Thus, the in-group for this joke are people familiar with the common definition of imaginary, and familiar with the fact that "imaginary numbers" is a term used by mathematicians. The joke being that, if they use the term "imaginary numbers", then someone came up with numbers that don't fundamentally exist, and they were only used to cheat out an answer to a difficult problem. Of course, in math this isn't the case, the numbers most definitely exist. To me it just seems like you're trying to be a pompous know-it-all and ruin people's fun, but you can't even do that correctly because you didn't understand what the joke even was.
Imaginary numbers were originally no more than an ephemeral reasoning tool, and were only reluctantly accepted as entities in their own right because of how damn useful they were.
That, there, is the story of pretty much all maths. There were occasional mentions of zero and debates about whether it's a number or not in old Europe, it only became widely accepted once base 10 became popular. And people still can't agree whether the natural numbers contain it!
Hah. Church tried to ban it because it was "associated with illegal money trading", I remember that. What is it about maths that makes non-mathematicians think themselves qualified to judge matters they don't understand?