I'm genuinely disgusted when Christians use "just have faith" (or words to that effect) to deal with issues being raised. Technically, it's a valid response, but by means of cultural implication, it becomes invalid.
The latter first: The cultural implication, of course, is "don't think about it, don't worry about it, just trust that it's all good." This attitude isn't very biblical, and doesn't prompt people to actually consider what the bible says/implies about an issue, or to think/talk things through. The whole "blind faith" discourse defies the majority of demonstrations of faith within the bible, so that should be a hint.
Now, "have faith" could be an appropriate response if it were meant in its full meaning ("just have faith" is still problematic, though, when the biblical meaning of faith is understood). There are several concepts wrapped together in the term faith. This includes trust, but not ignorance. On the contrary, one of the concepts tied into faith is theological reasoning. This closely ties into two other concepts within faith, which are 1) a knowledge of God as He's revealed himself, and 2) an expectation (based on this knowledge and aforementioned trust) of God's present and future behaviour (in particular promises being fulfilled) based on said knowledge. So, to have faith, or, as would be more relevant for dealing with issues as they arise, to develop faith, encompasses developing knowledge of God and trust in God, causing developments in expectations for God.
This is still terrible pastoral care, though, for the same reason that when someone's struggling to lift more weight or run further, it's terrible advice to tell them "lift more weight/run further" as the solution. "Hey, I really need an extra 10lb of muscle, but nothing I'm doing works. I'm frustrated and stuck and don't know what to do!" "Oh yeah, you should try gaining more muscle mass. That should do it." "Wow, thanks, I never thought of that! What helpful insight, you wise, considerate person!"