I've been member of a lot of critique groups over the years. With only one exception, I valued each and every critique, even if I thought it was wrong, or when the critique was just a scattering of smiley faces. Their comments or glyphs--as a whole--made me a better writer.
To keep a critique group healthy, the critiquee (the official writerly term is "victim"), must shut up and listen to the critiquer. Not explain, not clarify, not defend. The basis for this "shut up rule" is that a writer can't be standing over every reader's shoulder to explain what they really meant. If a critiquer says some passage doesn't make sense, maybe it doesn't make sense.
I just recently dropped out of my critique group because the "shut up rule" wasn't followed. Frankly, I don't care if a writer rejects my advice. My comments are opinion, not truth. My issue with defensiveness is that it wastes way too much time.
One group member would always respond to suggestions with long, drawn out descriptions of back story--not in the novel. Another member spent a lot of time telling us what would happen in the next chapter and how that would fix the problems in the current one. She would also say "Since two of you said this was a
problem in my manuscript, it must be a problem." Like critique is the same thing as an election. When confronted with her defensive behavior, she told us her other
critique group knew that she wasn't being defensive when she did stuff like
that, so she assumed she would always get a pass on the shut up rule. She was defensive
about being defensive. She would also grunt her approval or disapproval at critiques directed to another member. I absolutely hated that.
Anyone who's in a critique group should, of course, decide if the critiques are valuable. Take it or leave it, burn it or worship it. But they should do it on their own time. If a victim requires postmortem analysis or cleansing rituals, they should do it afterwards, not during.
rationalizing or interrupting during a critique group meeting insults the process.
Psychology Today: Do You Get Defensive When You Get Feedback?
For a great example of how not to respond to critique, see: Why Isn't My Book Selling? 1/1 Jihad Britain