I didn't mean to dispute that the texts present this as a quote, just to point out that it is Diogenes Laertius presenting it out of context, so more than just relying on him to present it accurately, we're relying on him to have judged the context correctly
Hmm. If that's the concern, we would arguably have to throw out the majority of fragments and even Cicero since he also didn't necessarily cite context but cherry picked what he wanted.