"낚시하는 남자가 누구인지 압니까?"
Translation:Do you know who the fishing man is?
Do you know the man who is fishing? 낚시하는 남자 - the man who is fishing/the man who fishes. The fishing man makes no sense.
Whilst it may not be the most natural way to say it, it definitely does make sense.
Fishing before man qualifies it. He's the sort of man who goes fishing, probably what we'd loosely call a fisherman. Fishing after man modifies it. He's a man who's doing something to do with fishing. Surely this should be, "Do you know who the man fishing is?" Fisherman seems to be 어부, fishing man 낚시꾼 at least in the dictionaries.