If you can't argue in the affirmative of the other side, you probably don't actually understand the topic to being with, and are probably not very good at critical thinking.
This also happens to be one of the most (holistically) effective techniques irl when “debating” with someone.
"Tear it down!"
"OK, but can you give me a good reason to?"
"...It's an obstruction."
"Reeeeeal persuasive."
Even if the other side has abysmal reasoning, you won't be able to distinguish that from decent arguments if you blindly try to push your side of things. Besides, establishing common ground is key to cooperation.