Jiho,
I guess , "hair growing the wrong way" means that something is wrong or something is not going the way that it should or not going the right way...
I guess the other members may be able to throw more light on this..
Thanks, Shalstudent, you are right, the sentence means something is wrong with the guy that has the hair 'that way', and i guess that, if this is not an idiom, it should be just a colloquial way to say it and nothing more.
Context: London mid 19th educated guy speaking:
«Charles' old friend must have the hair growing the wrong way»
and then explains some proffesors' dispute.
Thank you!