It is crucial to retaliate immediately. Don’t give your brittle intellectual honesty any time to muster its forces.*
Under no circumstances send an email or post a comment along the lines of “Thanks for your detailed critique. I rarely get that, and it’s a bit overwhelming. Given some of the things are quite precise and critical, my ego is flaring up. Rather than respond now, I am going to ponder for a couple of days. I am posting this to let you know I did read what you wrote, and will give a considered response within a few days.”
This would be FATAL to your secure view of yourself, and you would then have to follow through on self-reflection. No, no, no.
Start your insta-reply with a ritualistic “thank you for your critique” sentence. You then get some high moral ground (even though everybody knows your “thanks” are a manoeuvre).
As they used to say in the CIA, Admit Nothing, Deny Everything, Make Counter-Accusations.
Admit that mistakes were made, but not by you. For example, if the event under discussion started late, do NOT say “As the speaker, I could and should have prompted the chair to get things moving. I will do so in future.”
Make excuses about how you didn’t complete your presentation until shortly before the start time. Do NOT say “In future, I will take responsibility for my time management and get things sorted in advance.” Do NOT say “In future, I will ask the chair to give me a five minute warning, and then will wrap up on time.”
Strawmen are your friend. If someone has said that a presentation went on too long and had too many slides, answer as if they have taken an extremist “opposed to ALL powerpoint on principle” position.
Make vague references to “well documented importance” without reflecting on how your presentation may not have met the basic standards that are, um, important.
Dismiss the person who has written the critique as either not expert or not relevant. A sentence like “Somebody from your background was not really my target audience” should do the trick nicely.
Dismiss the person who has written the critique as incompetent. Point to a factual error in the critique, without considering how, if someone with English as a first language who was taking contemporaneous notes got it wrong, then the depth of misunderstanding among people with English as a second (or third?) language who were NOT taking contemporaneous notes might conceivably be a smidgen higher.
Cite every single people who told you they had a good time. Ignore the fact that they may well have been obeying social norms, just being polite, or have Stockholm Syndrome. Do not reflect on how many of the people you didn’t speak to were pissed off.
* And if your comment doesn’t go up immediately, send it again. The evil critics do not have day jobs (how do you know? Well, just guess), and are obviously imperialist colonialists who can dish it out but can’t take it.