Half feels right. The moral median is forever moving up. I can trust most people in a room to avoid murdering, robbing, raping, or engaging in political conversation with me, so that’s my rationale.
Pareto principle works here too. It's like 20% are decent, 60% sit on the fence depending on context, and 20% are always awful.
These ratios are more strictly 20/80 the older the sample sets, ie roughly 80% of people over 65 are toxic, in most cases, even when their behavior hurts themselves.
The parts of the brain responsible for social behavior don't fully develop until adulthood, and the brain gets rewired substantially during puberty, around middle school age. So, a middle schooler is seriously handicapped when it comes to social behavior.
Whenever I ask myself why kids shoot up their schools instead of CEOs, eventually I think back and remember what middle school was like and withdraw my curiosity.