If someone, especially one who pretty much worked for free for 20+ years to make YOUR PRODUCT BETTER and you just burned off all their hard work in front of them, just publicly quits with a proper explanation given as to why, and then you ask them to come to a quiet corner to "discuss things", maybe as damage control or whatever, without returning the favor and explaining your point of you as publicly as they did, or even preferring up the chance to give them some sort of agency and an opportunity for yourself to rectify things, I cannot see anything except condescending and disrespectful behavior.

This doesn't need any low-context/high-context nonsense to figure it out, given when the complainer's post was plaintive enough for someone from the Netherlands to appreciate.