Yes, "zero tolerance" is a simple-minded ethic, but I think we all have ZT topics, whether it's Jeffrey Lebowski and The Eagles, me and olives, or police and sass. They go by other names, such as "red flags," "dealbreakers," and so on.

It sucks that in the gun/murder example it would ruin someone's life, and I would advise them to be more thoughtful if I could, but there's no accounting for taste.