LOL This could be what is going on, but, the same 'actions' in the chinchilla world are also used to decide who will be the dominate or alpha/boss chin. This could be his way of saying "I'm the boss around here!" Especially when the action is to your hand or arm. This can be a way of 'claiming' you as belonging to him.
We have one female chin that has claimed my husband as hers. If Bill and I hug or kiss in front of her, it makes her mad (jealous) and she will spray me every time I pass her cage for the next 3 days. Even getting her a mate did not stop this. ( Guess she's in love with my hubby.
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As far as his "barking" at you when you make him stop, could still make his actions a show of dominance or one of 'affection' ... neither of which, is it acceptable (by a chinchilla) to be interrupted by an outside party ... it is understandable that it makes him mad.
Having him neutered would not be the answer. 1) Neutering or spaying of a chinchilla is a very delicate operation.
Unless the vet is highly qualified and very experienced in this area, the results can be devastating. Chinchillas rarely react to surgery in a positive way. 2) If the actions are not sexual in nature, but only a dominance issue, the actions will continue regardless of the surgery.
If it is a dominance issue, when he tries it with your hand/arm and you make him stop ... you are showing him you are the boss, not him.
Jo Ann