The problem isn't advocacy, but quoting. They did use [brackets], so I hesitate to call the quote outright falsified, but since brackets are intended only for clarification, their use in this case is definitely deceptive.
They shouldn't tell lies about history. If a particular historical figure said something, say what they said, and don't put false words in their mouth.
Do you not understand that what ACLU did was showing deliberate contempt for the idea of truth itself?
> There's virtually nobody who quotes the US founders who is actually advocating for the precise same set of values and institutions those founders supported.
Yes, and that's fine, provided they quote them accurately and not deliberately misquote them.