If I have full custody of my 8 year old child and his father has not wanted or attempted to see him in 2 years until now, do I have to make my son go see him?

Absent some court order to the contrary, if there is not order issued by the court allowing visitation or custody rights as to your son's father to your child you are under no legal obligation to allow the father to see your child. I suggest that you may want to consult further with a family law attorney about your matter.

You state that you have full custody.  If you have full custody because of a court order, then that order will control.  If the order only provides for visitations at your discretion or supervised visits, then you would need to allow him access, but you could require that the visits take place in your home (or some other safe place), while you are present or close by.  If your orders do not grant him any access, then you are not required to give him access. 

Conversely, if the orders do allow him regular, unsupervised visits, then you need to comply with those orders.  However, you mention some things that are disturbing... specifically a recent prison trip and prior assualtive history.  Considering these factors and that he has not been in this child's life for over two years, you could file a motion with the court to modify the custody paperwork to restrict or deny him access to your son. 

If you have full custody, but there are no court orders in place, then you do not have to let your son go with him.  Until there is an order in place, you both have equal access to the child-- but his rights do not trump yours-- so he cannot compel you to turn over your son. 

If you do not have orders in place, you may want to consider applying for them.  If you son is with a sitter one day, his rights would trump the sitter's and you would not have a ready mechanism for getting the child back.  If a court order was in place, you could file enforcement and contempt actions to secure the return of your son.