They appear to have lost any sense of proportion about anything.

They worry about what the OW might be 'suffering' while trashing their families

They stay in a long long marriage and then inform us unblushingly that they were never happy. WTF??

They tell us they love us, but aren't 'in love' and then behave in the most hurtful and ridiculous ways imaginable.

We could all go on, and on, with examples

There is no proportionality in anything they do.