You can evaluate a persuasive technique insofar as you talk about its likely impact. You might talk about whether the technique was profoundly important to the writer's argument, or if it was more of a subtle way to point the reader in a certain direction, for instance. A normal reader doesn't say to themselves 'oh look, the title of the article rhymes, therefore I will agree with the writer', but they might say 'oh, this writer works with homeless people, therefore what they have to say about homelessness is valid'. It is good to show an understanding that not all persuasive techniques are equal to each other. In that way, you can talk about the extent of the impact.
It isn't about arguing whether the techniques were good or bad, just about how they effect the reader - no writer will deliberately write something which is perverse to their contention.
Disclaimer: I'm not familiar with the ESL course.