I've read this thread with a certain amount of bemusement over some of the emotional reactions it seems to have generated, and it saddens me a little, so I hope you don't mind a few comments from an old curmudgeon with decades of cycling experience (and built on the experience of much-loved father and mother, and grandfather, who cycled their paths before me and taught me so much).
Until I returned from my break and joined in this forum, none of my family's three generations of cyclists had ever heard of the idea of having a "winter bike" because good ones are only for summer (I've never asked them, admittedly, but I know them well). Many things have changed since our old days, but I'm confident that the chemical properties of iron and aluminium have not changed much since they were first forged in those ancient supernovae.
So, a claim by a bike shop bloke that you're not supposed to ride your good bike in the winter or it will corrode is obvious nonsense.
Yes, of course, iron (steel) and aluminium will corrode, and yes, of course, salty winter slush will make that happen faster. But it's all about the rate that it happens, and what we can do to slow it.
If you want your new bike to remain in pristine showroom condition with no sign of ever being used, well, hang it up in a gallery somewhere. But if you want to ride it, and keep riding it all year round, some basic preventative maintenance should keep it going for many years, through rain, snow and salt.
I used to ride a 531 steel bike all year round, to work and back every day, including through some pretty obnoxious winter weather. My standard procedure was to always carry a can of WD40 in my bag, and if my bike got wet on the way to work or back, I'd give the exposed components (brake mechs, derrailleurs, chain) a good spray. It's not lube, it's not a long-term solution, but it appeared to work very well for displacing the water and keeping corrosion away. Then, if it had been a wet or dirty week, at the weekend I'd clean the bike properly and re-lube.
I've still got that bike, and after a bit of work on it last year, it's still going strong.
I wish my granddad was still here, because I'd love to tell him that some bike shop bloke has claimed it's normal for a new bike to rust in just a few weeks if you ride it during the winter. Unfortunately, I can't share with you my mental picture of his probable response
Alan