Where has he said this? The top of http://mi.wikipedia.org/wiki/Wikipedia:Community_Portal states very clearly that every article should be written in Māori.
Yes, yet he states at http://mi.wikipedia.org/wiki/User_talk:24.251.198.251 (and various places on sm:) that since "English is the first language of at least 80% of people of Maori descent", that English content should and will be kept.
Isn't he referring to content in the Wikipedia namespace there, not articles? Where has Robin added English content to articles?
Have you discussed this with any of the people who have edited this Wikipedia? There are 75 registered users and 8 admins. I'm not aware of any of them having a problem with Robin's approach, which as far as I can tell simply involves adding explanations in English to some pages in the Wikipedia namespace, and a pointer to that explanation from the main page and site notice.
See http://en.wikipedia.org/wikistats/EN/TablesWikipediaMI.htm
In the last 30 days, only 3 people have been very active: Robin Patterson with 62 edits to the article namespace in the past month, Rocastelo with 72 edits to the article namespace in the past month, and Vardion with 12 in the last month.
Robin Patterson is, as you know, the most prolific contributor. He is not of Maori heritage, and his level of Maori is (self-admitted) mi-1.
Rocastelo is from the Galician Wikipedia. Nearly all of his edits consist of adding interwiki links and, more recently, images from commons.
Vardion used to be a bit more active on the website. As far as I know, he is in a similar position to Robin Patterson (non-Maori), although I think he's more fluent (not sure).
Māori is certainly not the only Wikipedia doing this. http://kn.wikipedia.org/ also has English in its site notice and that project has many native speakers of Kannada and is about to reach 1000 articles. http://gu.wikipedia.org and others do the same. The Arabic village pump contains an English introduction, and the early discussion in the project was mostly English
Discussion in English is not an issue. Discussion may take place in any language on any Wikipedia. The issue is content outside of the Talk:, User talk:, Wikipedia talk:, etc. namespaces.
Kannada, Gujarati, and other Indian languages only have English in the site notice for one reason: because many peoples' browsers cannot display the languages, so it is nessecary to give installation instructions in English. It is likely that these will not be removed in the near future, as disemination of Indian language font technology is relatively slow-paced.
With Maori, however, there is no such issue. Well, some people do have troubles displaying letters with macrons. Yet, the site notice doesn't mention that.
As Anthere mentioned here and Snowdog mentioned on my talkpage on the Tibetan Wikipedia, increased or exclusive use of the appropriate language in a Wikipedia is ideal, and in fact it usually attracts contributors (Georgian, Armenian, Haitian, Limburgish, and others only became active after I did a rough translation of the Table of Contents).
Anyhow, I cannot emphasise enough the attitude of my Maori friend, and the fact that most Maori speakers will be less likely to contribute to a "Maori-language encyclopedia" if it has so much of its content in English.
Particularly upsetting is the fact that the first words -- the very first words -- on the mainpage are English, followed by Maori, rather than vice-versa. This is not an atmosphere indicative to a newcomer of an encyclopedia which aims to be in the Maori language.
Examples of him promoting English on content pages: http://mi.wikipedia.org/w/index.php?title=Taurepo&diff=7155&oldid=71... http://mi.wikipedia.org/w/index.php?title=TTA&diff=6106&oldid=3415 (ip is anonymous version of him, I think) http://mi.wikipedia.org/w/index.php?title=Aotearoa&diff=7157&oldid=7... (not promoting english, but rather a site he is affiliated with... the links were later re-removed by another anon) http://mi.wikipedia.org/w/index.php?title=Template:Stub&diff=1788&ol... (not promoting english, but here he notes that his maori is not fluent)
Mark