I find this a pretty unconvincing analysis of the "X is murder" type arguments and "taxation is theft." My linguistic intuitions are pretty strongly on the side of all of those claims being false, or at least open to debate.

No one outside of extreme libertarians ever refers to taxation as theft, as far as I can tell.

And the reason we have a word "murder" that's separate from the word "killing" (or even "homocide") is that murder is taken to be, by definition, unjust. There doesn't seem to me to be anything too-clever about saying that, any more than there's anything too clever about saying that canines are a particular type of mammal.