If anyone still think bitcoin to be a scam, I do not think the person will be able to realize what bitcoin is actually again, many says bitcoin is a ponzi while many says it is a scam but they are all wrong. I hope they will not miss in the next bull run before they will actually understand what bitcoin is.
There's still a chance, he/she just need to be educated.
If I'm not mistaken, accusations of scam is due to its volatility in Some instances wherein their expectations are not meeting the reality of easy profit. The impression of Bitcoin is profit to investors who are not really aware of the nature of this market industry. Also, it is being used in fraud projects and schemes which left a mark to other people who just know Bitcoin by hearsay. We just need to tell them how this market works and I'm sure they will be interested afterwards.