How do I Reset a User's Reputation?

One of my users has been having issues with people giving all his posts bad reputation simply because they do not like how he acts. This is not acceptable behavior on my forum, and I would like to reset his reputation. However, I see no option to do so in the reputation menu of the ACP or in the users menu. How might I go about this?

On a side note; is there any way to tell who is abusing the system and giving bad rep to all of this user's posts?

It is not possible to reset it.  Even if you turn it off and on again, it does not reset.

Also there is no way to tell you gave positive or negative votes.

There are some codes that remove the negative vote.

Like SLG said there isn't anyway to reset the rep system.