It is a constant cycle that can be picked up at birth. Girls receive pink blankets, while boys get blue. Societal norms shape and mold gender discrimination into a common, respectable way of life. Repeatedly, it has been illustrated that women are the weaker sex. This philosophy begins to form one reason as to why many support gender discrimination.
Women are simply physically and biologically weaker to men.
As for sport, they should not be placed in an environment in which they do not fit naturally. Many view women in sport as looking silly and not a serious competition. Men are physically able to compete at higher levels and it is natural. Another perception is that women do not hold a competitive and mental attitude to compete at high levels of sport. Society again tells us that a competitive woman is unfeminine.