I wouldn't consider it an insult at all, I am just saying it's simply incorrect. I'd argue the same point if someone said that Lexus vehicles are only slightly nicer than Toyotas.
And for the most part, that's exactly what Lexus's are, and it's usually a major knock against them. Why buy an expensive Lexus when a loaded Toyota will be almost as nice and cost less? Like Infiniti, some of their models differ in drivetrain (FWD vs RWD), but they share a lot of the engines/transmissions, and some of the interior bits of both premium brands remind you of those in the mainstream brands. Say what you want, but when you sit in a BMW or M-B, you don't think of 'shared parts bin' engineering.
So MB and Chrysler have never shared parts??
The fact that you are basing your Nissan/Infiniti statements on absolutely zero experience or personal knowledge is what I find baffling. That's like me saying a G37 uses better interior materials than the 335i even though I've never even sat in a 335. See what I'm saying?
Sure, Chrysler borrowed many parts from M-B, notably platforms to build the 300, and even the new Grand Cherokee. But you won't sit in a 3-4 year old C-class and find a part that's in the Sebring from the same year.
And I'm talking purely of interiors, no need to drive an Infiniti to judge its interior. And as I said, I'm mostly basing my opinion on the horrible interiors of Infiniti's of about 7 years ago. Things may have changed drastically since, but when looking at recent pictures, I still have the same perception of back then. Whatever, I'll stop now.
I'll be interested to see how the G25 does in North America. I wouldn't be surprised if it's a short-lived experiment, to be honest. Either that, or they slowly creep up the prices for the G37 every year, essentially making the G25 a better deal. We'll see.