Dragons are jerks

1. They'll take your stuff. Dragons are massive hoarders, and they don't usually care if the stuff the take already belongs to someone.
2. Their sneezes will singe off your eyebrows. Dragons do not know how to cover their mouths, and have this horrible habit of breathing fire.
3. Dragons are hypocrites. They demand that you are respectful to them, yet they treat you as inferior creatures not worth wasting manners on. How rude is that?
4. They have huge appetites. Dragons will eat almost anything and anyone, without feeling even the tiniest bit sorry about it. So keep an eye on Fido.
5. Dragons will wreck your house. For a dragon, no party is over until the walls come crumbling down. And if you don't invite them? They'll still come crashing through the window.
6. They hold a grudge. If you upset a dragon, they will remember you. And they will do their best to make your life miserable from then on.
7. Dragons don't share. Need a few more pieces of gold, or a rusty sword? Don't ask a dragon for help, because they will snap at you for even suggesting they give you something. And a snapping dragon is not good for your limbs.
8. Dragons lie. Just like their stuff, dragons guard any knowledge they have obtained. Ask them for directions, and they'll direct you somewhere completely different then where you want to go.
9. Dragons are grumpy. A dragon is never in a good mood, and they will let you know exactly how unhappy they are with a blast of fire.
10. Dragons steal princesses and other damsels. They'll carrying away a girl, and then keep her locked up for no reason whatsoever. It'd be one thing if they needed a maid, or someone to shine their scales. But most dragons abduct fair maidens just because they feel like it.