Yep , just a rule that lacks insight to how it happens under match conditions and in real time. If a defender was tackling with their head as per NFL or Nate Miles for those of you who have watched a bit of State of Origin, then they deserve a red card.
The idea of an accidental head contact being a red card is just a bit too much. Rugby is a contact sport , you sign up knowing that , occasionally someone contacts the area above your shoulders. If it’s intentional or careless there should be a sanction , if it’s just an unfortunate collision it should be shelved as part of plying a contact sport. Players know what they are they are up for, they all are happy to lead with their upper body/head to score a try off a pick and drive from 1 metre out , that’s rugby ……