Here are several reasons this is a better way to express our Biblical mandate to be salt and light both inside the Church and to the unbelieving culture.
Faith, when Biblically understood, is a perfectly good word, but, we (the Church) have allowed the word to be misunderstood and marginalized by our culture.
The first or "common" definition most people think of is the ability to believe in something that has no proof, or, perhaps, even to cling to a belief in spite of apparent contradictory proof. Blind faith. Is this Biblical faith? Absolutely not! Using the word, faith, just tells the world you are part of a marginalized minority and should be ignored.
Another common perception of faith is that it's more like flavors of ice cream than insulin. Our relativistic society sees faith as a personal preference, not a truth claim. You can have your faith and I can have my faith ... whatever works for you. To claim to "stand for your faith" is to start off swimming upstream against public perception.
Truth has been relativized, too, but nowhere near the degree of misperception of faith. Everyone, even the relativist, lives as if there are some moral absolutes - i.e. truths - and it's much easier to tackle this with logic and reason than to set everyone straight on faith.
Claiming to "stand for truth" has a much greater potential for starting out on more common ground without having to fight the battle first over misunderstanding of the word, faith.
Ultimately, you have to talk about Truth, anyway, so why not just start there.
" I am the Way, and the Truth, and the Life; no one comes to the Father, but by Me." John 14:6 (NASB)
I would even go so far as to say there is just as much confusion over faith inside the church as out. Using words like truth and trust can enable us to bring clarity to the murky waters.