to give it a try :P Most likely if someone believes that the 20% rate is a scam, he/she will also believe that Hive in general is a scam and that you can't earn at all. If it's a random person we can't do much about it, we need better marketing and ways to educate them.
If it's a friend of yours or family, then it may be easier to convince him/her, and show him some monthly stats and graphs that exist showing that people actually earn per month. Also, they can start with a small amount even 1$ and see each month or even each day their earnings. Even if let's say the rate drops to 15% or 10% or even to 0% still nobody will lose their initial investment. Only if something goes completely wrong then not only HBD but Hive in general will get dumped, which is the usual risk anyone faces with any kind of investment. They can also simply hold hive and earn %2.9-3% APR!