One phrase: the responsibility of the one being hit. Hockey is a contact sport, and hitting is an integral part of it. In order to keep that aspect in the game while ensuring the safety of the players, everyone must
1) avoid throwing hits that threaten the health and safety of the other player, and
2) avoid putting themselves in a position in which their own well-being is in danger, should they be on the receiving end of a body check.
In this instance, Kulikov violated the second rule: Hertl had him lined up, but due to Kulikov turning at the last second (he did see Hertl coming, mind you), the situation turned into one in which both players suffered. What was supposedly going to be a legal hit on Kulikov became an illegal one, all due to his moronic play. It is debatable whether Hertl intentionally broke the first rule, but there is no question about Kulikov's wrongdoings.