Your friend would have to be very firm with him in regard to the needs of the child. If he does not have a whole lot of experience with children and is not able to ensure that there is not a whole lot of disruption in the girls routine, then your friend may suggest that if he takes her, the visits are shorter. She can have him extend the length gradually.
As far as him being bad, it is more an issue of how experienced he is being a father and dealing with a toddler. If there are any parenting classes, he may benefit from taking some. The little girl would still need to have a father. Even though right now she's somewhat confused about him and his role in her life, there will come a time when she would know who he is and may want to have a relationship with him. It is a better idea for her to become familiar with him as a father figure starting now (especially if he seems to want to be involved in her life)
He sound not only inexperienced but proud and not wanting to hear other's input. If she has grandparents (his own parents) perhaps your friend may mention to them some of her concerns (especially if he brings the little girl to their home)
It is not shameful to take a parenting class (he of course has to be willing to do it) If your friend believes that he may agree if she goes with him, then she can offer to do so. Have her also write a list of what things he would have to do when his daughter is visiting (not a long list but the basics and for her to write down the girls habits; ex: how she likes to eat, when she usually takes a nap, what activities she enjoys, movies etc.)
Your friend must stress out to him that little children do well with routines and when they know what to expect. She can let him see that it would be helpful not only to their daughter but to him as well. If he refuses to go to a parenting class, your friend may try to find a good DVD for him to watch (perhaps before he picks her up at his next turn. If she is flexible, she can have him watch it in her home while she is getting the girl;s belongings)