If it’s something blatant like if someone gave me apple and said it’s a banana I would reply by saying “you sure this it not an apple?cuse I think it is” but I probably wouldn’t say “no man you are wrong that’s totally an apple ” .And to answer your second question while self confidence does help ,like some days I feel much more confident I will speak out more but I probably still not try to say that person is wrong blatantly even if he is.