Well, as long as he knows the deal, I don't see the moral problem with it. But I think one of two things will happen:
1) It won't be much of a practice because it's hard to fake liking someone so lots of elements that you might want to "practice" won't happen because your feelings aren't involved or
2) You'll end up liking him after all and so you won't be pretending
I'm real doubtful that you can seriously date him in a pretend girlfriend way and continue to not like him but at the same time have it be a legitimate analogy to a real relationship. But that doesn't mean I think you shouldn't do it. Just adjust your expectations of what this is. More practice dating than a practice boyfriend.
But oh, if you think he is the type of man that it's not good for you to be emotionally attached to (e.g. "kang" type, or anything else you object to), I don't suggest you try to pretend girlfriend or whatever. You may end up being more invested than you anticipate.
Thank you, this also puts things into perspective. I guess my issue is that I won't date anyone that I couldn't see myself marrying. I am pretty new to the dating life, but I picky. I guess I should not date this guy if I am not attractive to him. He is a borderline kang, but he is funny and can hold an intelligent conversation (although it is mainly me schooling him)...Why can't I find a hot nerd? That would definitely be my type.