To not answer questions put to you after you pretend to be a master debater.
not answering questions, especially loaded or irrelevant ones, is a great debate strategy.
edit:
while i think they are picking a semantic fight about a topic on which they are not prepare to engage, your engagement has been kind of shitty toward them, too. i think you could be better and still show that they are silly and ignorant of the topic.
1, voting is not harm reduction, and 2, that video has given you a false conclusion. the lesson we should learn is that strategic voting leads to party consolidation, and the only way to keep third parties is to continue to vote for them.