I might have misphrased it. Don't trust those with conflicts of interest essentially - that doesn't mean treat as always wrong but keep in mind what they have t

I might have misphrased it. Don't trust those with conflicts of interest essentially - that doesn't mean treat as always wrong but keep in mind what they have to gain from pulling one over vs being honest - and keep in mind people aren't always rational and can fall into 'stupid evil' traps. If one is pushing an idea on its own merit in a standalone way they are more trustworthy than one doing it and shilling a book. That said if there are other reasons to trust you certainly should keep them in mind.