Responses
He has reason to be afraid of them when their existence is higher than that of the King's, but its a selfish reason. Its why the readers oppose his views. When trying to understand an antagonist, you have to try to see why they're the protagonist of their own world. That helps make a story that much more enjoyable when you can understand everyone's point of view.
The dragons fought hard and shed blood to protect the country. It's great that people are finally giving credits to Yona and the dragons for their effort, but the more well-known the dragons are, the more dangerous it is for them. People are greedy and will try to capture these dragons for their selfish desires.
Also, that damn advisor. Is he even allowed to act without the King's order? Investigating and chasing after Yona and the dragons without permission. She's not thinking of reclaiming the throne so can't these people just leave them alone?