Face it, guys, these people are right to be reluctant.
What has the worst safety record? Private flying. Maybe you have 50 hours,maybe 350 hours. That's not a lot compared to how long you've been driving a car. Persuade your chums to have a proper lesson with a pro instructor, and stick to flying with fellow pilots who do know and accept the risk and can actually be useful in the right hand seat, like helping with lookout, nav, and RT. AND share the expenses.
Newbie pilots (and old ones too) who like to show off and turn their passengers green, should be tied down on a perpetual roller coaster and covered with vomit.