Using that logic, I could just as well argue that since you don’t pay me to debate this with you, you don’t deserve a reply from me, since I am not your indentured servant.
In other words: There exists roles and relationships, with attached obligations and expectations, other than those involving money. Free software development is such a relationship, as is this debate.
If you were to post rude comments in Hacker News, you probably wouldn’t get a response, because it would be delete. It kind of proves the very point you’re opposing - being polite begets good responses, rudeness to being ignored.
I have zero expectation that you’d reply. Most conservations on hn don’t end because they wrapped up neatly but because someone had something more important to do and walked away from the conversation.
There are obligations other than money, but none of those exist here. There’s no contractual obligation. He put out something for free and doesn’t need to take an iota of criticism on it by people freeloading. He obviously can, and if he wants certain goals like increasing his user base it might be the smart move to respond to these type of people, but there are no obligations.
A social obligation, in short, is something which a person would be rude not to do, but is not required by law. I’m sure you can think of examples. I am putting forth my opinion that fixing bugs, regardless of how rude a bug report is, is a social obligation.
HN is one of the best places on the internet to politely post a critical or opposing view and get a reasoned response though; doesn't that strike directly at your point? Perhaps that's exactly what I'm doing righbt now, because you weren't a rude jerk? ;)
