If you know CRM then by all means you should avoid a personal conflict.Do your job,keep quiet and monitor the flight. Safety should be your first concern,and in any case avoid wrestling over the controls. A calm ,neutral tone combined with pertinent remarks will be your best asset.I'ts not easy all the times,especially if you are a young FO.
The CRM tells that the worst possible combination is a hard ,tough captain combined with a shy,introverted FO.Avoid beeing like this by knowing very well what your value is.Do not try ,though,to prove your qualities to one another.
All the best.Safe flight
Alex