I'd like to point out some historical examples of how that argument has been used time and time again to push aside any attempts at diplomacy and justify what in hindsight were plainly needless wars of aggression, but which seemed quite justified to people at the time (at least when it started).

I think many of us have more complex views on the conflict, but most people aren't interested in hearing us out or learning about this history of the conflict, so it's easier to just say, "Look, practically speaking, Ukraine doesn't have the capabilities to reclaim all their territories and it's just going to cause a lot of pointless death if they tried." And I do believe that's true, but I'd still be calling for peace if I didn't.