In my opinion, the most crucial ramification of "doubt" is its ability to stop someone from achieving the things he/she had always wanted to. The eyes of doubts people unintentionally or intentionally show could unkowningly create a barrier between one person and his/her destiny. I'd seen plenty of that and honestly, they are hard to ignore. They discourage, they put people down. Despite my belief that we shouldn't care about what other people think, the fact that they still sting remains.

Therefore,
Show grace. 
Show mercy.
Show people that you believe in them, truthfully.