I had an argument with a friend just yesterday, who seemingly believes that Bitcoin is being controlled by a single entity and Bitcoin is not secure.
He said a lot to back his claims which although I can't remember his pin points though.
I knew once that he doesn't really know much about Bitcoin so I decided to back out of the argument.
Misconceptions like this are merely caused by lack of education (Bitcoin related) and sometimes education in general.
There even might be people in this forum who have similar misconceptions, the question is how do we tackle this misconceptions?
There is no other way of tackling something than to let the person know the advantages of bitcoin. You will let him know how useful bitcoin is and how it can help people, including him, if he believes in what you explain to him because that is the reason why he keeps arguing with you because of the knowledge he lacks, so you will be the one to let him understand, although people that have this type of mind set towards bitcoin may continue to see it this way, so most of the time you will allow them to be because you can't change their mind set towards bitcoin.