Indecent? Assuming it's the picture I've seen then it's funny but hardly indecent. All you can see are a couple of hairy buttocks almost side on. I've had women in the past send me worse. Maybe I should try to find some and insist they resign.If you were running a business based on having high professional standards and your main public facing employee has an indecent image of himself circulating online then there is a conflict of interest.
In this persons case I think it will come down to the circumstances. If he has done anything wrong then he should be gone. If not, then he shouldn't (although I suspect his career will be over either way).