This quote is not meant to justify being a debatebro with chuds. The quote is meant to mean that you should not be a petty with your comrades. It says that you should not be toxic in circumstances where arguments are warranted, specifically for "unity, progress, or getting work done properly". It doesn't mean you have to debate every person.

The list is prefaced with "liberalism rejects ideological struggle and stands for unprincipled peace". Being a debatebro against chuds creates of an environment of unprincipled peace.

Mao certainly did not say "Debate fascists lol".

Who ought to be rewarded? Those who resist Japan, those who uphold unity, those who are progressive. And who ought to be punished? The collaborators and reactionaries who undermine resistance, unity and progress. Is our country now unified? It is not.