I think the old Denmark law allowed bestiality that did not cause harm to the animal. They are modifying the law as in many cases, it is difficult to demonstrate that intercourse caused harm. Violators of a law that allowed some bestiality based on the animal’s consent would be unpractical, if hilarious, to prosecute in court.
If we are to compare child sex and animal sex laws, we should take into account that we are allowed to harm animals in many ways that we are not allowed to harm human children. We are allowed to kill cows and turn them into burgers, and we are allowed to sneak up to a deer and stab or shoot it. However, somehow, it is illegal to bang the cow or deer and let it go unharmed.
This is why I concluded that bestiality laws are primarily meant to regulate human behavior that people would consider creepy and weird.