The basis of arguing or debating effectively is using objective evidence to justify opinions, rather than relying on assertions that are based on logical fallacies. Understanding a logical fallacy is an immensely empowering skill.
In language, the way we express our views, whether we are very certain, or somewhat less certain, is frequently shown through modality. It is an integral part of persuasion; sometimes present overtly, and at other times less obviously expressed.
You can think of a speaker as an artist or craftsperson and ethos, pathos and logos as the framework upon which the artisan works. Hone your own knowledge of these rhetorical tools, and how to recognize and appreciate them in speeches you study.
Propaganda can be dangerous when it is used on an uninformed public: people are easily persuaded because they do not have counter-arguments to the information they are being given. You may think you are immune to propaganda – but living in a digital age does not always make it easier to detect the techniques involved. It requires a conscious effort to be critical, work on your media literacy, and to stay alert for argumentative fallacies.