In order to revoke without tyranny, imprisonment is NOT sufficient. This applies to religious vassals as well as feudal vassals. There's 3 ways to revoke without tyranny:
1. Have a claim on the title
There's various ways to do this , but the most straightforward is using your chancellor to fabricate a claim.
note: your chancellor cannot fabricate on a barony-level title, e.g. a bishopric
2. Target ruler is your direct vassal and is a traitor
This can be caused by the target rebelling and losing (or white peace?), or by the target refusing your request to stop backing a plot.
note: barony-level titles(e.g. bishoprics) will never rebel
3. Target ruler is of a different religion (and your realm laws allow it)
Depending on if you have the Conclave DLC and what realm laws you have passed, you may be able to revoke from vassals of a different religion. If you are able to obtain the title above your target and give it to a courtier of a different religion, that heathen (or infidel) will replace his vassals (including your target) with rulers of his religion . Once he's done, you can revoke your previously appointed title, and that (prince-)bishopric is now your direct vassal and ruled by a heathen! (or infidel!) From there you can revoke without upsetting any of your proper, god-fearing vassals.
note: Religious revocation does not allow Christians to revoke from non-heretical Christians. e.g. a Catholic can revoke from a Cathar or Muslim, but not an Orthodox
note2: If granted title does not allow religious revocation, you have to wait for your pet heathen to convert his vassals