Another possibly unpopular opinion: having some bad people makes us safer on the whole. If the world were perfectly safe, and we didn't have to study and invest

Another possibly unpopular opinion: having some bad people makes us safer on the whole. If the world were perfectly safe, and we didn't have to study and invest in security, redundancy, weapons, emergency response, and so on - we become more vulnerable as a race to potential future badness. Phrased differently, if badness is physically/theoretically possible, we're better off having to practice defending against it, than be caught off guard when it does manifest later on (by natural events, aliens, whatever). Similarly with war, there is likely some optimal level above zero that increases our overall safety as humans by honing our abilities in force.