Its a great shame that the two of you need get so heated - so David thinks that Gursky is the best thing since sliced bread
Actually... I don't

I just can't imagine why anyone would say he's crap.. or, to be pedantically correct here... worth 50p. I like his work, but he's never been someone who has consciously influenced me. There are MUCH better photographers out there... but he's FAR from crap, and I admire his work.
while Dean feels that its not something he'd give house room
There's the problem: Judging work by whether you want it on your wall. That's simply not how art is judged. I wouldn't want it on my wall either. In fact, most of the photographs I admire I wouldn't want on my wall.
Neither of you is right or wrong - its just a matter of opinion , so why not just accept that people can honourably hold differing opinions and move on - calling each other names adds little to the debate.
Because if I posted up images of birds on twigs, aeroplanes taking off, babies in baskets etc.... and started a thread on how crap they are... well, you can imagine what would happen. I accept such photography has it's place, use and clients who happily buy it, which is why I don't bang on about it (except eye watering HDR.. which genuinely is baffling). What gets me riled is the amateur habit of "Look how crap this is... I can't believe people buy this rubbish" attitude towards anything they don't understand. The evangelistic pounding of this drum just gets wearisome. It genuinely is reverse snobbery in it's worst incarnation.
In essence, I agree with you completely. Some people like photography as art, some don't. I just wish people would consider that "like" doesn't not equal "worth". People don't invest large sums of cash in art because they like it, they do so as an investment. People don't invest money in businesses because they "like" them either, they do so because they see a return on their investment one day. It's the same thing. The art is immaterial as an artefact. I don't respect Gursky BECAUSE he sells work for millions, but people invest millions in him because people like me like it. Why can't people see that? So the price of a Gursky is pretty irrelevant to this debate.
Personally Gursky's work is not to my taste and my opinion errs more towards deans position - not that I necessarily believe that all good pictures have to be pretty , but as I said above I do believe that a work that seeks to communicate a message should do so through its visual impact , not through a heap of accompanying verbage and interpretation. as Gursky's shot fails that criterion (in my opinion) its not something I'd want to put on my wall , even if I had £4M going begging.
It's really simple. A man was obsessed with capturing a view of the Rhein. He couldn't because all this stuff was getting in the way. So he removed it in order to capture the real essence of the scene his imagination saw. Simple as that. There is no verbage. Concept.. solution... statement. Quite simple. How is that of less value than a baby in a basket?