Faith gives a person a certain power and confidence, a comfortable and secure belonging to a group that one trusts, and the fellowship that arises from that association.
But the sharper edge of the sword is that faith can also drive a person down a narrow path that does not respect other points of view, with a severe purpose that is stubbornly unshakable. In many contexts, this kind of determination can manifest as a good quality that will deliver successful, sometimes incredible results.
In some cases, however, blind faith can drive people to seriously harm non-believers outside their circle, and also members inside their circle for purposes of accountability and enforcement.
The disastrous irony of blind faith is that it motivates people to do harmful things that, in their heads, they believe are good, right, just, noble and necessary to serve the principles of their faith. The whole thing about faith is to believe things for which there is no empirical evidence. What can you say to a person like this to convince them otherwise? Heads are chopped off in the name of faith; horrific never-ending wars are waged that kill thousands.
I ask you, is there a more powerful and sharper double-edged sword in our world than blind faith?