Yeah, I have lots of "evidence"; that is what I do all day - gather evidence to implicate Canonical in trying kill Linux :-)
Seriously, I think these are valid questions to ask and discuss if we do it politely. The consensus between those who responded is that Canonical is benefiting the Linux ecosystem and I agree.
I do however think think that there are two different alternate realities here. One is the overenthusiastic reality which you see at tech sites and discussion forums (e.g. Slashdot), and the other is the actual physical reality.
For example In the physical reality I have never met a person who actually uses Ubuntu. When I say "uses", I don't mean install every new version and "try" it, but actually use it for everything on his home/work PC every day. I am sure such people exist, but they are much fewer in absolute numbers than one would assume by reading tech sites. (I myself actually _do use_ Ubuntu on my laptop 100% of the time, but people think I am crazy. We also tried to use it on desktops at work, but alas that failed).
On the other hand, I have met many people who have a Ubuntu Live CD, or a partition, which they boot probably once a month. This is a fake user base. Their primary OS with very few exceptions is Windows. These are probably the people who upgrade their Ubuntu every 6 months - I am sure that nobody who actually uses their computer would be crazy enough to do an upgrade so frequently.