Are they correct to argue this, in your opinion?

Hell no! They duuuuumb. Lol. My point is that even if you were going to canonically "answer" that question you have to deal with the fact that you're talking about a fictional universe and you will still have fans and writers who disagree and wind up stretching that to its breaking point. Them coming out and authoritatively stating "R2-D2 isn't a real boy" solves as much as Rowling authoritatively stating the house elves really enjoyed slavery. It's just gonna piss people off.

Conceivably in our future and in SW’s past these debates will be / were solved civilizationally. SW is very inconsistent but presumably they landed on ‘chatGPT3PO is only a sophisticated mimicry of life’, and the prejudice against them might be more to do with them being used as powerful genocidal weapons a generation prior than a class anxiety because of droid labor

Sure, but that doesn't mean it's a universally adopted perspective and/or that it's even true. I personally think that star wars as a fantasy setting is far more interesting if the sentience of the droids is left ambiguous and inconsistent.