-they don't understand it
-they have read so many confusing side of btc online that aren't true
-they are once a victim of scam,
-they have relatives/friends who have been a victim
-they are naturally hostile in nature 
one of the above must have occurred for anyone to be hostile towards btc, that's why it is always good to do one's own research and not rely on what you read or hear, if i had followed what i read, i won't be in crypto today, it is always good to learn.