Just thank them for the time but you have selected another position. Don't explain unless they hire you as a management coach.

Is your anger petty and spoiled? In absolute terms, yes, obviously.

E.g., I regularly saw a guy working at a rental car desk and commented on his always sunny disposition. He said he came to the country* with the promise of an IT job but it was a lie. Now, he can't get out and his boss told him to always smile or he'd be jobless (and thus homeless with a high likelihood of starvation).

Are you Spoiled, Petty? Yes, but many of us are.

Doesn't mean you should take the job. Just be grateful for your circumstances.

*I won't divulge the country. Don't bother guessing.