The fear of criticism,
the fear of ridicule,
the fear of scorn,
the fear of rejection,
the fear of not being appreciated or belonging,
fear of a lack of esteem,
the fear of self-actualization.
We have been conditioned and controlled from infancy to seek and value the approval of others, a kind word, a thoughtful gesture and if we feel a new idea will trigger laughter, or cause us to feel foolish afterwards, we just keep our mouths shut.
(It is also useful to remember that ideas that originally sounded ridiculous usually become the basis for all major breakthroughs.)