My opinion: (Could be completely wrong... :$)
1. Allow the goal to stand, you have given advantage as the striker has got away from the man fouling him. Don't book either player (they're both sending off offences, but if you send off one and not the other there would obviously be uproar, and you can't send off the defender, because it was a goal :S)
2. If both captains agree, move ends.
3. Issue a second yellow card, followed by a red for unsporting behaviour. (Surely pulling your shorts down is worse than taking off your shirt Calum!)
Other comments on the website:
1. If the forward intentionally elbowed the defender before the ball entered the goal (which I assume) then stop play and disallow goal. Send off forward and show yellow card to defender. Free kick for defence. If elbow is deemed accidental, play on and YC defender after allowing goal.
2. Move the kicks from the penalty spot to the other end of the field.
3. Show scorer a yellow card for unsporting behaviour and show red card for 2 yellows.
1) Goal stands, defender red carded for dangerous play. No action on attacker, accidental contact.
2) Move penalties to other end, but all penalties must be retaken.
3) Second yellow card shown, Red card and player sent off.
1) Goal, red card for defender, and pretend the elbow thrown was accidental, since it did connect with Gary Neville's face, after all.
2) Move penalties to the other end.
3) Second Yellow/ Red.
1) Assume elbow is accidental (striker was off-balance after being dragged down by the defender), allow goal, yellow card to the defender
2) Move to other end of the pitch...both captains are in agreement
3) Second yellow card, leading to a red, and send him off.