Okay. I have a hot guess and no clue, if it's right or I am just seeing things.
I thought the "Armand told the truth" bit was just an in universe Edward vs. Jacob thing.
But now we see it plastered on the wall of a lair of the fang gang (?). Louis is there (I guess it is in the house we see in the new trailer, where Louis drives up to) and I guess he got in there to kill.
So they believe something Armand said. But I think the book is a red hering, because I can't pinpoint anything from the book that would justify this extent or attacks on Lestat.
So my hot guess. "Armand told the truth" in this context is something we don't know yet. I am reaching here, but maybe this still is from an interview setting. That he is telling the truth about something here.
And he also warns Daniel (You are courting great danger with Lestat). He knows something.
Wanna scream in the comments with me about this theory? :D I am going bonkers.