Tell me if you've been in this situation. You're with a group of people and this one person has taken upon him/herself to "entertain" the group. For some reason or another, it's usually guys who do this. So while a conversation is in progress, this guy keeps shooting in with really bad jokes. And I mean bad, they're obvious, they're stupid, you see the punch line a mile away and you just wish you could excuse yourself, which you can't, or zap the guy into a pile of dust, preferably. So the guy is telling these jokes, and some people are laughing, but not everyone is. You're not laughing, because you're appalled with what can pass for a joke with this guy. So the guy notices this and he says to you, in front of the group, "hey lighten up, have a sense of humor". Have you had this happened to you? Of course, everyone has.
But what does it mean to tell a bad joke? When I say bad, I realize it can mean more than one thing. A bad joke can be one you don't laugh at, because it's too obvious. Or you don't laugh, because you don't like making fun of whatever is the butt of the joke. Or some other reason. In this case, I'm sticking with the first definition. So the joke is too obvious. Now, if you'll indulge me for a minute, the following metaphor I borrow from one Jerry Seinfeld. A joke is a canyon between two cliffs. If you get the joke, you jump across the canyon, onto the other side. If you don't get the joke, you don't make it to the other side. The satisfaction from making it, is the laugh. Now, if the cliffs are too far apart, you won't make it, it's too far away. If they are too close, you make it, but it was easy, so there's no satisfaction from making the leap. So in other words, the object of a comedian is to set the cliffs far enough apart so that the leap will be big, but not too far apart, so that the audience can still make the leap.
But let's get back to telling bad jokes. What is a bad joke really? No, what is a joke really? A joke is a sequence of statements which are logically coherent with each other. If A, then B. If B, then C. And finally, at the end of this chain, there is a contradiction. Something which doesn't add up with everything that has been told up to this point. And that is the punch line. Why is this funny? I've no idea, but this is the anatomy of a joke. Now, the degree to which a joke is funny, is the lack of coherence between the punch line and the story the precedes it. If you can see that the punch line contradicts the story, then it is funny. If you do not see the contradiction, it means you don't get the joke. Once again, a bad joke is one where the contradiction between the story and the punch line is obvious.
So, a joke is a test (yes, a test!) of reasoning ability to see whether you can see the contradiction. You pass the test, then you laugh (or you don't laugh because it was too obvious). Now, a bad joke is simply a test which is too easy. So what does it mean when you tell a joke, what does it say about you? It says that you are giving this test to me, and you expect me to pass it. You would like me to pass it, with some effort, so that I will laugh at the joke. Now, if you make this test too easy, it basically means that you believe this easy test will not be trivial to me. It means that by giving me this easy test, you expect me to struggle a bit.
So let's say that the test is easy, the contradiction in the joke is obvious. How can I interpret this? Well, there are two obvious ways. 1) You think this joke is clever, and you think I will appreciate that. 2) You realize this joke is obvious, but you still think it won't be obvious to me. In the first instance, it doesn't make you look good, it makes you look a little stupid. In the second case, it's an insult to me, to think that I wouldn't find this obvious.
So there it is, telling a bad joke is one of two things. Exposing your lack of intellectual ability (and ambition). Or just being patronizing.