[s1t5]

> But fails to mention the the moral reasons to choose oat milk over cow's milk.

This is kind a red herring. Cow's milk should be irrelevant because you don't have to choose between the two. You can leave both out if you have moral reasons to avoid cow's milk and health reasons to avoid oat milk.

[rattray]

The author compares them to each other, so it makes sense to talk about why you should take it out of the picture.

As it happens, though, unsweetened almond milk does seem to have much less sugar – 0.2g by one measure I found (another just says 2g carbs of which 1g is fiber) and a glycemic index of 25 (low).

So it is a bit surprising that the author didn't make this comparison – it's much more favorable to his point.