Hizb-ut-Tahrir openly works for the restoration of the caliphate, the supranational center of Islamic unity. In classic Islamic theology, only the caliph is authorized to declare offensive jihad against non-Muslim states for the purpose of subjugating them under the rule of Sharia, Islamic law. In the absence of a caliph, as has been the case since Ataturk abolished the caliphate in 1924, only defensive jihad may lawfully be waged — which is why jihadis today always frame their activities in the context of alleged enormities of non-Muslim entities.
Note the book that the Islamic supremacists fear at 2:30 of the Australia video — my own The Truth About Muhammad! (Thanks to Kamala for the heads-up.)
Thanks to Pamela Geller for the videos.