A lot of scams have caused the fear of theft among people and they are regarding bitcoin and its trading a scam. People seem to be reluctant towards investing in bitcoins. How do we ensure them that bitcoins are not scam but the people are. 
We can make them understand that bitcoin is not a scam by explaining to that 'people' (you're referring) about the unforrunate cases of using it like there are a lot of greedy people that actually scattered in here that the main objective was to get your money. In that way, they will conclude that it is actually a person who refered as the 'scam' and not the bitcoin itself. In addition to that, tell them that bitcoin is a mere cryptpcurrency and doesn't have enough capacity to scam you because it is not its factor and function.