I also pointed out 2 out of THREE of his reasons were becuase of premades.
Actually one reason was that PUG is at a disadvantage to a premade, which is pretty much 100% provable fact. In the OPs argument this means that a lot of good players who don't have pre-mades will have lower ranking.
The second reason was that players playing Pre-made vs Pre-made will lose more. This means that a lot of good players who play in premades can also have a lower ranking when they choose their opponents. This is supporting Pre-Made players who play in leagues, not against PUGs, so your flaming was unneeded.
Most of my losses in custom have been due to fighting in bad PUGs. I turned to Pantheon and have an almost 100% win ratio, I have a loss from a drop. So that means that either
A) people playing in Pantheon are all really bad (could be quite true)
B. playing in a matchmaking service where Premade is impossible evens up teams and that I am not that bad a player
C) that there are no bugs in Pantheon, which in custom are causing the majority of my losses
Personally, I go for a little of A and B. A lot of hardcore players are playing in premades and so will be in custom, not Pantheon. Never playing against a Pre-Made makes chances of winning a lot higher.
Leading back to the original argument that the stats are pretty useless as determining a players skill. The biggest factor at the moment would be that pre-made groups (even when you meet another good player randomly and team up with them next game) in custom are at a huge advantage to pick ups.
Losses to bugs are actually minimal, if they were a factor, surely your stats would reflect that, unless you are suddenly impervious to bugs and have the holy grail of Demigod clients.
Now there are no problems with Pre-Mades per se, I wish I had the time to find one all the time. However, Stardock does need to take on the fact that players need better matchmaking. Pre-Made game queuing/clan matchmaking and solo player ranking match-ups for starters (which I believe they have and hopefully will be with us shortly).