Dads act very protective to their daughters because they fear seeing them get spoilt. They are afraid about bad company and they care about the safety of their daughters out of the experience that they have earned in their lives.
Dads love and protect their children, boys and girls equally in most areas. However, simply put Dads, were once boys. Dads can remember. That is why they have a super "protective gene" when it comes to their daughters.