What is the ruling on saying "Amen" to every supplication except for the supplication made for the Sultan or ruler?

It is permissible to supplicate for the Muslim ruler so long as there is no extravagance in it. Some scholars have deemed it disliked to supplicate for the ruler, unless the supplication is for rulers in general, which is then encouraged. However, if the preacher fears harm to himself, it is permissible for him to supplicate for the ruler. Therefore, one should say "Amen" to the preacher's supplication for the ruler if it is legitimate, and there is no sin upon whoever does not say "Amen."