It doesn't really irk me. It just doesn't interest me as wine.
When someone asks for Chablis like that, that's a clear opportunity to educate that person in a helpful way. I'd ask "Are you looking for French Chablis or American white wine?". Odds are, in 9 out of 10 instances, if you're friendly about it, the customer will ask "French Chablis?" and you'll have an opportunity to explain the difference. It's a good idea to fastidiously avoid passing judgement in this case.
Odds are they'll still want American white wine but they'll better understand the difference.
It's also a good segue to mention the naming issues with champagne and hearty burgundy :-).
One would think otherwise it was fermented in larger bottle and transferred to smaller bottles, or it was fermented in huge tank and artificially carbonated...
Heh. Sparkling wine. Most people get the meaning. If you're mentioning it to a customer, you can even say "even though the state says we can call it champagne, we prefer to call it sparkling wine out of respect for our French comrades in Champagne" or somesuch.
Most customers don't need a lecture, most customers are happy to learn new things when not made to feel stupid in the process.
Dana