splitting threads

Have you noticed it? -- a new usage creeping in and taking over that's replacing 'who' with 'that'?
That's doing this? I mean, who is? Is it the zeitgeist that's (who's) lessening our contact with the human and veering us ever more towards the non-human? Or maybe, the anti-zeitgeist??

It was my ninety-year-old uncle, since deceased, who first brought the trend to my attention. In his penthouse flat in Cheltenham he folded over his copy of the Daily Telegraph (a fairly right wing newspaper, so you would expect traditional English usage) and handed it to me.
"Read this, Brenda, then tell me what you think."

So I did, and realized I'd been coming across the use of 'that' rather than 'who' quite a bit in North America. I told him that (or do I mean who?). Piercing but faded blue eyes held my gaze for several seconds. My uncle didn't say anything, but I knew exactly what he was thinking:
What is the world coming to?

Good question.

I merely told him that (who) had to be deliberate. They must have laid it down in the Daily Telegraphs style book, so likely it was here to stay.