It depends really on what kind of "forced to change your beliefs" situation it is.
Is it a situation that forcibly changes reality or one that simply removes an option.
If the first... Bahá'í Islam probably... or some sort of Judaism.
Buddism is great and all, and a great thing to model your life over... reincarnation is not a very preferable afteralife if you ask me.
If the second Agnostic. Religion isn't something that you change based on choice.