I would leave it out, as some people would (incorrectly!) making a character judgement call.

Leaving it out would not result in any gaps in his working history, as you said he was working fulltime.

Depends on the type of new job he is applying to. You could just leave it out, as some people would (incorrectly!) making a character judgement call.

Leaving it out would not result in any gaps in his working history, as you said he was working fulltime.

The plus point about leaving it in would be showing that he worked 2 jobs. And because it is legal it would make an interesting talking point when he does get an interview.