In debate, and whenever else a believer might be challenged on their beliefs - there is often the temptation on behalf of the believer to refer back to their beliefs as reasons why they hold those same beliefs. This is the 'faith' rebuttal. Here's an example:
A: Why do you believe that Jesus was resurrected?
T: Because the Bible says it is so.
A: But why do you believe what the Bible says?
T: I have faith that it is true.
A: I know that, but why do you have faith?
T: I just have faith.
Now, theologians practically make a living out of glamorizing faith and imbuing it with all sorts of connotations, but ultimately faith is just another way of saying 'I trust it'. Even if the theologians are correct, all they are saying is that faith is a special kind of trust.
Normally trust is something that is earned. The process of earning trust is through justification. I trust bridges won't fall down because of the observed safety protocols that are enforced, knowing that an inspector can be held morally and legally liable if they fail to detect structural defects in the bridge, I trust in the innate human tendency to want to avoid getting caught not abiding by duties and being morally culpable for the consequences. The bridge safety system has, in short, earned my trust through closing bridges at the first sign of potential trouble.
Theologians would argue that faith is a mystically unfathomable type of trust. What it seems to boil down to as far as I can see is that faith is special because it doesn't need to be earned. Indeed, faith seems to be homeopathic trust: The less justified the trust is, the stronger the faith is.
By promoting this unjustified trust, faith is seen by many to be a virtue. Con artists rely on exploiting unjustified trust. By thinking that faith is a virtue, you are creating a Trojan Horse of the mind: Clever people may successfully exploit your belief in unjustified trust, to your detriment. You may get off lightly, and merely end up believing in some strange things, but is it worth the risk?
Finally, there is something infantile about saying you believe what you believe because you have faith it is true. It reminds me of
A: Why did you punch B?
A: But why?