It depends on how Dwarven laws regard freedom of speech I suppose. Attracting a Great Dwarven Philosopher could counter him, spreading rumours could work.
Of course under current mechanics, players could just drop a ton of rock on him any time they want so there'd need to be disadvantages to doing so. Unhappy cult dwarves, unhappy Dwarves who had the need to regularly argue with the Great Goblin Philosopher, unhappy Dwarves who feel goblin minorities aren't being represented well enough etc.
I wonder how far keeping secrets from the player could go in the future?
The other issue is what would cause a dwarf civ to make free speech legal or illegal and how much freedom do we have as a site government either to prohibit the Great Goblin Philosopher or to allow him to operate.
LAW in my view should work to reduce the player's scope of freedom, a society with high
[LAW] places legal restriction on what the player can autonomously do about the problem, one with low
LAW leaves more things to the discretion of the site government.
[POWER] on the other hand is the value that promotes censorship. The more a society values power, the more it sees the Great Goblin Philosopher as a problem that can be solved by making an example of him rather than a problem that will solve itself. The two values intersect as following.
High
[LAW] + High
[POWER] = You have to punish the Great Goblin Philosopher.
Low
[LAW] + High
[POWER] = It is up to you to deal with the Great Goblin Philosopher how you wish.
High
[LAW] + Low
[POWER] = Freedom of speech is legally protected and you cannot punish the Great Goblin Philosopher.
Low
[LAW] + Low
[POWER] = You can punish the Great Goblin Philosopher but it will make you unpopular.