Deciding to flee this town, possibly forever is something hard to accept for most of these people here. Something regarding pride doesn't really let their subconscious accept fleeing because of a weird tree, even though that tree caused all this damage and can suck the soul out of them.
Of course here is where Eric, as the ruler of this town comes in. No one can directly refuse his commands according to tradition and how things go here, the best they can do is advise him to do differently and that's where their freedom of speech meets an end.
Its not like they would be punished if they refused, here it would just be dishonourable. Furthermore since Eric is considering their well being and fleeing is possibly the best decision, this tradition is working to their advantage.
