Why, because the proper use of analogy give insight to how things work where it was not before.

Telling the robot analogy to a person bagging parts in a warehouse would make a lot of sense to him. Just saying 'security attack' and his mind will probably wander off in imagination of ninjas and pirates kicking in the door, murdering everybody, and running off with all the products.

The problem with that analogy though is that it rather long and convoluted for such a simple concept, a simple direct explanation would suffice here. I feel that there are two problems with it: 1) it's completely removed from what a real SQL injection is - sure, it's analogous, but then go to whoever received that explanation, present them with a form and ask them to tell you what each character in that tale is analogous to. 2) It's not succinct. Someone who isn't interested in knowing in the first place wont appreciate the verbosity. ....and someone who is interested will appreciate a better and more direct explanation.

So we shouldn't teach those wanting to learn more about a particular topic...? I don't understand your abrasive attitude towards someone trying to learn more about a topic.