Countries like Iran, whose governments believe they have a handle of the truth, think that possession of truth means they can suppress all wrong.
This all goes along swimmingly until the great truth the country is based on becomes increasingly unvalued and questioned.
Surely it is better for truth to have dissent permitted? For how else can we know and value truth?
If one is so sure one has the truth then one has nothing to fear from allowing dissent because dissent and debate all help us, if we are honest, to see truth more clearly and to value it more dearly.
If you think it is only countries like Iran that need heed freedom of truth think again.