I hate it when my T does that. It feels as if you're not being seen as an individual person.
But I also tried to see it from a T's point of view. Sometimes they may not know what to say or how to react or what to do...
And then I guess it's easy (doesn't justify it of course, but...) to look back at another example and start comparing it. It's just the way we learn, by seeing examples of good and bas stuff and then eventually learning about values and ...
So I wouldn't be as angry as I would have been before anymore, if it would happen (again). If my T would still keep my situation and my personality into account of course.

Could it be that your T was a little bit stuck? Or really wanted to make some point clear and found the only option was to work with an example?
If he/she did still see that you are you and not that other person, I'd try to talk about it and ask about how T is seeing things, until you understand and your anger may fade.
If your T really treats you as if you're the exact same person, I'd be angry too, yes. And I believe you should be too. Nobody should be treated that way.
Since you say your T has been amazing through all those years... I really hope it's a misunderstanding between you both.