Can't see the problem here. I assume he has a valid reason to be wearing non-standard footwear, in which case under the circumstances the shoes clearly strike a reasonable balance between comfort and smartness. Indeed, there are clearly worse footwear he could have chosen to wear. It isn't like he is wearing white sport trainers!!!
At the end of the day, I'd rather my plane leaves on time with a full crew roster, instead of the plane being delayed due to one crew member being offloaded for incorrect footwear. First world problem, much?!