Right which is ad-hominem. A debate tactic that people more often use unintentionally than intentionally. Even when there is no actual disagreement present. Not only that, the "why is this particular matter so important" or "you seem to be taking this matter very personally" is a very common ad-hominem tactic.
The fact is that in discussions, we respond to something being said. We make our points. Then people respond making their points. Then we respond back. etc. It's never that a particular matter being discussed is personally important. It's that all matters being discussed require logic, listening, understanding, interpretation, feedback, etc.
If somebody makes a statment that you consider to be invalid. You give the correct explanation and proceed with productive discussion if necessary. It doesn't matter what the subject is. One isn't necessarily more important than the other.