Same with anyone else. You should have responded with much more humility knowing that you are a newbie rather than responding aggressively. My points is he may be wrong but you are also in the wrong. If you just accepted your mistake and move on this might not have happened at all.
Don't think being a newbie gives you the entitlement of doing mistakes freely.
With your price, you should have thought that if its can caught in the wild, don't expect much price in the first place. To give you some background, most players sell decent IV's paired with good nature caught in the wild for ~10k(e.g. gastly with speed nature bonus and ~80 total iv). Now if you consider dratini in kanto, since its not readily available and mandatory to acquire super rod from the next region before even getting to catch one and you also need to pay 5k for 20mins in the area where it spawns, it is usually sold for 30k+ regardless of nature and IV.
Note that what I said above doesn't represent everyone's view on price. It's just based on my personal experience.
EDIT: Btw the community is not that bad :D. It's easy to find someone to trade evolve without losing your pokemon hehe.