Perhaps some of them take it too far, but it's at least an interesting perspective, in light of stuff like the post and your experiences in Ruby.
I do agree in general that you have to be sure to consider the external dependency as a cost, and the benefit you get for it better outweigh the costs. Exactly how you determine that varies from language to language quite substantially, and probably varies by personal taste and experience level too. For instance, you might be less inclined to take an external dependency for something you find quite easy to write yourself, whereas someone not as skilled may find it preferable to take the external dependency if it means they don't have to learn the nuances of whatever it is enough to write it themselves.