This is an example of bad poor graphical representation. The proper way to do this would be to take the swear words per word for each language and then map this to a bar graph, then you could easily see which has the highest vs the lowest.
A pie chart is good for things that add to 100%. The number of swear words that occur in something is not appropriate for this type of graphic.
Considering that there were an equal number of commit messages for each language, this is a perfectly adequate representation. In this case, the pie chart's total is the number of swears, with each slice representing a language's share of that.
You’re entirely correct, except for this: The pie chart applies here because the author made no attempt to correlate number of profane commits with number of commits, total, per language. This post means literally nothing, so he could use whatever graph he damn well felt like.
A pie chart is good for things that add to 100%. The number of swear words that occur in something is not appropriate for this type of graphic.