I totally get what you're saying. But as an Individual I personally am fulfilled when I succeed and unfulfilled when I "fail" it's not something I can really change, it's my personality. You might not be like this which is totally fine.
Ultimately, its about behavior. If I do poorly, I won't be happy, I won't be having fun. As much as misery love company I'm not going to allow myself to behave in such a manner that I'm ruining other peoples days. If you beat me, even if it's a donk, or by a bad ruling, or good luck, I will never not offer my hand for a handshake. Likewise, when I win. I'm not going to gloat and behave like a bad sport making other people be upset.
The problem many people have with donks, is that my want to win, which is what I enjoy, gets in your way of your having fun, assuming fun for you means playing a good thought out game. So your interest in enjoying yourself conflict directly with that same interest in me. This happens a lot in society as whole. That's why we have rules in Pokemon, and laws in the real world. Which means that a person is only entitled to have "fun"(playing the actual game) if you are if you are willing to accept that both you any other opponent have the right to do what ever they like as long as it's with in the rules.
For a player like for example, I like winning, but as much as like winning I cannot stack my deck in order to do so, even if I would consider that a good way to achieving what I want. For, a player like you(I'm assuming here that you enjoy it when the game is being played with hard thought by both players not donk.) Then you have to be ok with me playing decks that you don't find fun.
EDIT: My ultimate point is that people should not be pissed at other players for trying to achieve their goals as long as they are following the rules.Being upset at the rules and wanting them changed, now that's a whole other thing completely legitimate thing.