Agreed. It's a shame that swearing has to spoil a potentially good resource. I won't be able to share this will my little brother, who could benefit from this while learning to code, purely because of the amount of swearing.
If you do not want to show it to brother, more power to you and you got my respect for thinking about what language he picks up. Really. However, the resource has exactly two impolite words in it, so it is hardly huge amount.
Maybe the author feels obliged to curse a little bit, and mostly in jest / for its own sake because the domain name includes a simulacrum of obscenity (WTF) in it.
It's just too strong for me to feel comfortable sharing it with younger ones. I guess a more accurate way to describe the issue for me would be to say it's because of the "strength" of the swearing rather than the quantity.
However, I will be sharing this with co-workers! It's a good document for reference.