Because individuals can be honest - and groups are not.
Any group in which dishonesty - i.e. anything less than the sincere attempt to seek and speak truth in all things at all times - is tolerated, is on the wrong side in the spiritual war (no matter how much good they contain).
(Dishonesty is - or should be - a sin for Christians; but it is not regarded as intrinsically wrong for most religions, nor for most atheists. Unless lying is a sin, then truth will only be attempted when expedient.)
This is the great probem of our times; in that there aren't any institutions that are honest: there aren't any that are even trying to be honest. Believing and obeying any institution will therefore lead to damnation; passive, unconscious, consensus living will lead to damnation.
No institutions are honest: certainly Not science or academia! But not the Christian churches either - as can be known from reading any paragraph of any press release from a major denomination.
As an individual, you can resolve to be honest; and you can follow it through (and recognise and repent your inevitable failures). In an actually-existing institution, this is impossible. Any honest institution would nowadays need to be a new foundation, including only honest individuals.
Historical experience suggests honesty is only possible for small groups under unusual circumstances - as happened in science for a while (this was the situation in the UK when I had just began as a scientist, in the early 1980s - but within a decade it had gone).
In a world of systemic and pervasive dishonesty; it is our Christian duty and neccessity Not to believe public discourse; since we know it is not-even-trying to be truthful. This is a duty that far too many Christians fail, spectacularly.