The CoC clearly speaks about harassment and not about personal lifestyle choices. If you keep your private life to yourself you should be fine.
Can a CoC be abused? Sure, if the community culture allows it. Does that possibility invalidate a CoC alltogether? Probably not.
A CoC will codify allowed behaviour which decreases the freedom for some forms of expression, most of which were destructive in nature and wasting everybodies time anyways. So in a certain sense you loose something, but you will also get something. Very talented persons who are to shy to use their ellbows all the time might be more willing to contribute etc.
IMO a ok tradeoff
No, it doesn't, this Drupal story demonstrates that COC are useful to get rid of people one doesn't like because they somehow "hurt" somebody by doing something in their private life.
https://www.inc.com/sonya-mann/drupal-larry-garfield-gor.htm...