IMO the main issue is that you're punishing (or at least inconveniencing) the person whose predicted to be bad. The 21 year old man did nothing wrong being a 21

IMO the main issue is that you're punishing (or at least inconveniencing) the person whose predicted to be bad. The 21 year old man did nothing wrong being a 21 year old man, and just because he's super suspicious doesn't mean he's actually dangerous. And you have to imagine what happens when you are the one who seems super suspicious. Similarly, 80 year olds and especially people with pre-existing conditions, they did nothing wrong, so it's not fair to make them pay more. Possible solutions are 1) monitor the suspicious individuals without inconveniencing them (e.g. monitor the 21-year old via a security camera), 2) distribute the inconvenience when possible (e.g. raise everyone's premiums a small amount for those who are more likely to be sick), or 3) offer some sort of compensation to people who have to be targeted.