What does "仗不仗义" mean?

Before you know the meaning of "仗不仗义", you need to know another two terms –
1. 伸张正义shēn zhāng zhèng yì.
2. 仗义直言zhàng yì zhí yán.
伸 : means stretch
张 : This word can be a name, and has many meanings depending on the word before or after. Here “伸张” means advocate.
正 : Basic meaning is square.
义 : Basic meaning is reasonable or right, but normally this word is combined with another word to form a clear meaning, like “正义” which means justice.
仗 : This word also has several meanings. Examples like war or depend on, etc. Here “仗义” means do something based on justice and rightness.
直 : means straight
言 : means speak, 直言 means speak out all you know.
Now, I think you understand the meaning of 仗不仗义, because it is
a saying combines “伸张正义(仗义直言)” and “不(No) 伸张正义
(仗义直言)” together.
Lastly, “伸张正义” and “仗义直言”, both are very formal and good
terms, while 仗不仗义, kind of casual spoken language, do appear in books describing the conversation. But seldom used in formal/essay writing -- Because it involves "yes/participate" and "no/don't participate" in one phrase.