Should I put a 6 month job on my resume?

It is better to be truthful about your career choices be it good or bad. However, it is advisable to accept the mistakes in the choices one has made and turn it into an advantage by accepting an error of judgment and reflect your confidence.
 
It reflects poorly if you omit and job and you are caught out during interactions or in reference check which corporate go in for. It is embarrassing and can easily be avoided.