It has nothing to do with sex, and everything to do with dominance.
Training: I would respectfully suggest you read a couple of books and watch some videos on raising and training dogs. Also, I recommend two TV shows, "The Dog Whisperer" with Cesar Millan on the National Geographic Channel, and "It's Me or the Dog," with Victoria Stillwell, on Animal Planet. Both programs are very instructive and often deal with the issues you raise here. Good luck!