Earlier quoted context omitted.
I've never laid people off, but I've fired them. It's hard to know what emotional tenor to put on it. On the one hand, of course you're right that upbeat positive optimistic is fake and maybe feels like it's more for you than them. On the other hand, being like, "this sucks and it's bad for you and I hated doing it" feels like kicking people when they're down, making them feel like it's even worse than it already is.…
Firing someone is the result of poor performance or unacceptable behaviour. In many jurisdictions (not in the US I suppose), before firing someone for poor performance they must be told that their performance is inadequate and be given a chance to improve. Bottom line, in general being fired is fully on the person being fired so no need to sugar-coat or to feel bad.
That doesn't mean the firing shouldn't happen, but it does mean that everyone feels bad.