I can understand use of force to enforce those aspects which are considered as violating the shariah law of an Islamic state but not all fall in that category. Zakat for instance, collection and distribution is the responsibility of the state and hence violation of the state governance in this case would invoke punitive measures. In cases where no Islamic state government exists, we are not liable to any punitive measures under the state law.
What kind of coercion is justified? So if one does not pray should he be whipped for it OR can we bouycott the person from society until they start praying? Which one is more effective on the psyche of the person.
Anyway, a Tyrant in general is one who uses force to have his way irrespective of the will and wishes of those upon whom he rules. In Islam it would be a bit different since our code of conduct is to follow Allah SWT teachings and guidelines. So neither the people or their ruler has the right to govern in any other way in an Islamic state. So one who uses force to eject the rule of proper shariah (emphasis on PROPER) would be a Tyrant.