Competition is fine for higher levels of the stack, like the desktop environments: we can have a 100 different desktop environments and all can still run the same applications, because they all use X and conform to certain standards... but in such an essential part of the system as the display server, competition is a bad thing and only causes division.
Canonical or not, again the company behind it has nothing to do with it. Try to think outside of your fanboyistic "us vs them" mentality. If it was Red Hat or whatever company doing the same thing, it'd be just as bad.
And yes, we have a bunch of different sound servers. That's exactly my point - do you want the Linux graphic stack to become a similar mess what the sound system is now? Can you honestly say that all the different implementations of sound systems are somehow good for Linux?
All the userland stuff - package managers, DEs - don't matter, there can be a 100 of them for all I care. We'll still have all the same software running happily together - but display server is a different issue. Is that hard for you to comprehend? That not all software is the same? In some cases, competition is good - in this case, it only causes problems and headache for everyone involved.
And yes, I used proprietary OS's as an example - not because they're superior in any way, but to highlight what a horrible business decision it would be for any OS to create two competing display servers. So instead of dismissing the argument in a stupid way, can you just tell me, why do you think it would benefit Linux to have competing display servers? What benefit do you see the desktop Linux ecosystem gaining from that competition? What benefit are users getting from it?