It's not about proving anything really. They are offering to fix the problem at hand, and merely asking for the faulty product to be returned. This is probably one of the most commonly acts done. If you received a faulty PV, you wouldn't expect to get a new one sent and get to keep the faulty one. My opinion is that you can't really draw the line here....a product is a product.
I don't think anyone was trying to come off that way wacko, but rather just give you some insight as to how the vendor may see things. I believe you found a hair in your juice. Why do I believe you? Because I have no reason not to. But, that doesn't mean that I don't want that juice bottle back so I can see for myself. Maybe I have 5 people working for me in my shop and I'd like to try and see who made up your bottle. Maybe I'd like to know this information so I can try and insure it doesn't happen again. Who knows, there are a ton of reasons they could want the product back.
Okay, I manage hotels by trade. This is a fundamental problem in the customer service industry imo. What you have presented them is not a voice of concern for the situation. I know you see it that way, but it's not so. What you have sent them is a request for a resolution. You were very detailed in what the problem was, but in addition, you added that you didn't know what to do. IMO, you left them no win/win response. If they just said "sorry", you would have been like "what?". If they did what they did, you are in the boat you're in now....somewhat offended. Had I been them responding, I would have pretty much did the same thing, but it would have been prefaced with "I'm extremely sorry this happened, and rest assured I'm going to look into the situation"....then proceeded with the options they gave you. I actually think they were spot on with the solution. They offered to replace the bottle, or since you mentioned somewhat of a put-off of the whole thing, a full refund. I think they went the extra mile with the solutions.
I'm faced with complaints frequently (some valid, some BS), and it almost never fails. They complain about this or that, I apologize sincerely, explain what I'm going to do to rectify the situation, and thank them for bringing it to my attention. They sometimes are happy with the response, and sometimes just stand there waiting for me to offer them something. It would be so much easier if I could read minds.
I understand how you're feeling about this. I'd be telling a lie if I said I'd never been put off, or offended by reactions I've gotten in the past...it happens. But, try not to take it personal, I don't think it has anything to do with you at all.
It's American mentality. A sense of entitlement.
That said American customer service sucks.