I see it used as a conversational gambit to downplay the impact of something you’re about to say (which might otherwise be received as over-the-top, or sensatio

I see it used as a conversational gambit to downplay the impact of something you’re about to say (which might otherwise be received as over-the-top, or sensationalised, or aggressive, or ripe for someone to argue with). It’s a bit similar to how one might start a statement with “Honestly…” - to flag that what’s coming might be more than usually challenging or blunt.