I'm a subscriber to Languagehat and read it every day. Among its posts I've found occasionally-fascinating nuggets about individual languages, interesting thoughts on language in general, and an inside perspective on issues in linguistics. However its posters do sometimes seem to display a woeful weakness for that kind of woolly, leftist thinking that particularly inflames me — not so much for its leftiness as for its woolliness.
You can see where they get it from. Their discipline requires them, on a regular basis, to talk to many different people, of many cultures, colours and creeds, often foreigners who live abroad (I'm flagging the danger words for you), sometimes even going so far as to speak to them in their own language! Worse still, they will often listen to what these people say back to them.
In this way, over many years, linguists can get to the point where they believe that most people are basically the same. That people half-way across the world are in many respects just like themselves and their neighbours. That the similarities between people are so much more important than their differences (except for really interesting ones, such as pitch differences between the sexes in normal speech). People all over the world are probably quite nice if you give them a chance.
Linguists are missing, then, the basic insight common to Loldemort and those like him (shameless and unrepentant homosexuals with a taste for corrupting married men, especially those who've proved that they've got lead in their pencils). Viz. that our neighbours are monsters who hate us, would like to write discrimination against us into the constitution (where applicable), and regularly indulge in legally-protected rants against us in church and mosque, synagogue and temple. The truth of course is that those smiling foreigners are, in their unique, irreplaceable and doubtless endangered way, just as horrible as our current neighbours are, have brains full of memes just as virulent as the diseases spread by 18th and 19th century European explorers were, and will do us all down in an instant given half the chance.
Now there's a particular kind of ego inflation that often afflicts linguists (who are invariably clever enough to be able to spell correctly in several languages, and who are regularly asked to rule on such matters of universal importance as correct punctuation, admissible vocabulary and the legitimacy of dialectal usages in polite intercourse), and that's to think that anyone gives a damn about their half-baked opinions on social matters.
The thought processes behind this post though, simply beggar belief. I imagine that we're supposed to think that English isn't the language of the land (of the USA) because — hang on, here it comes — it wasn't the language of the land a thousand years ago, and was subsequently imposed there violently. But of course, the cartoon "proves" quite the opposite of what is intended. The land doesn't care what language is spoken on it, only the people living there care. And if you let a bunch of other people come and establish their language as a living tongue in a substantial part of your language's range, without learning or using your language, then there's a good chance that your descendants will end up speaking their language and living in their world.