Ah, the good old "I don't like your gaming jargon, so it's wrong" :-)
"Toon" is a perfectly fine short-hand for Diablo characters in many player's eyes. And that goes back to actually *before* Diablo 1 (the term is over 30 years old). Read up on some of the history: Wikipedia, StackExchange. Now whether you personally accept "toon", like it, or hate it, is preference. But for someone who casually plays a softcore RPG-style WD in Diablo 3, "toon" is an absolutely fitting description. For a competitive, hardcore barbarian it might not.
For everyone there's gaming terminology that rustles your jimmies. For example, I want to kill anyone who uses "kk" instead of "m" for million (and I *will* edit it if you think "kkk" is okay instead of "b" for billion, for obvious reasons). As someone who played WoW (but only in vanilla) I'm very used to calling my characters "toon", but I hate it when my friends called their WoW toons by their kindergarden abbreviations: "dudu", "baba", and so on. Anyways. Yes, off-topic. I might split this into a separate thread, or find an old one to move those posts to.
/btt please ;-)