Why should the one receiving a generated answer when asking a person spend more effort validating it
Because they're the ones asking the question. You can flip this around and ask why should the person put time into researching and answering the question for OP? If they have no obligation then an AI answer, if it's right, is better than no answer as it gives OP some leads to research into. OP can always just ignore the AI answer if they don't trust it, they don't have to validate it.
Unsolicitedly answering someone with LLM generated blubbering is a sign of disrespect.
Fair enough, but etiquette on AI is new and not universal. We don't know that the person meant to disrespect OP. The mature thing to do would be for OP to say that they felt disrespected by that response instead of pretending like it's fine and reinforcing the behavior which will lead to that person continuing to do it.
It'd be like if someone used a new / obscure slur, the right thing to do is inform them how it is offensive, not pretend it's fine and start using it in the conversation to fuck with them . If they keep using it after you inform them, then yeah fuck them, but make sure your not normalizing it yourself too.
Meanwhile lying to someone to fuck with them and making stuff up is universally known to be disrespectful. OP was intentionally disrespectful, the other person may not have been.
The rest of your comment seems to be an argument against getting answers from the Internet in general these days. A person doing research is just as likely as an agent to come across bogus LLM content, and a person also isn't getting actual real world data when they are researching on the Internet.