Sorry, I realise this is going a bit off topic, but if you were reading a friend's new website and noticed mistakes, would you tell them?
This happens to me A LOT and I feel torn between not wanting to be rude, yet also not wanting them to look less professional by having mistakes on a public facing site.
I also see MN as a non-formal place where I expect to see typos (and sometimes they're hilarious so it's totally worth the judgements).
I would feel a bit more judgemental if I saw this sort of mistake on the BBC website however, and I have seen/heard many similar errors there surprisingly. Somebody once told me that as a journalist, it wasn't their job to write correctly, which I thought was a bit odd.
I think often people default to pointing out mistakes when they can't think of a better way to put someone down. Society in general has a definite tendency to judge intelligence based on things like this, which is unfortunate.
There are bigger issues here than simply people making mistakes and others pointing them out - issues of the quality of education, provision for those who learn differently, and how most of us judge each other based on things that are pretty ridiculous when you really think about it.