Given the focus on arguments that are alleged to be purely semantic, it would have been helpful to have a good example of such an argument. He describes the debate over abortion as a canonical example. The idea here seems to be that the debate over whether a foetus is 'alive' is a purely semantic dispute over the definition of the word 'life'. This strikes me as simply a mistake. It's certainly very difficult to have a sensible debate about abortion (and let's definitely not have one here!), but it's not plausible to characterize the disagreement between pro- and anti-abortion folks as a mere disagreement over the meanings of words. In the case of disagreements that are truly merely semantic, it's possible for each side to either (i) come to an agreement on terminology or (ii) agree that they disagree only about terminology.
Perhaps the broader issue here is that everyone loves to tell themselves they're leaving a community because they're too good for it, rather than just admitting that's it's become bad for their mental health to get involved in frequent anonymous arguments on the internet.
Perhaps the broader issue here is that everyone loves to tell themselves they're leaving a community because they're too good for it, rather than just admitting that's it's become bad for their mental health to get involved in frequent anonymous arguments on the internet.