I don't know to what specific number you refer, but my sense of our colleagues on this forum is that most of us would not tolerate this nonsense (including, if I may be so bold, you).
No boldness required. I've said so myself, and on this very thread.
However, I can't count the number of times I've heard forumites say things to the effect of "I'm not a babysitter."
Assuming that the OP is on target in hu's discussion of the classroom dynamics, and that includes many instances of out-of-control students, this OP is absolutely correct in being upset and in expecting hu's professor to actually be in charge of the classroom.
I don't doubt but that the OP is giving a faithful rendition of events. But I think that you are taking that faithful rendition, and assuming some zoo-like atmosphere where all hell is breaking loose.
There was consistent chattering.
Some students came in late.
Some students left mid-lecture.
The end.
Then, one day - and on one day alone - there was a big, albeit short, brouhaha, caused in part by the OP himself.
This is not grounds for dismissal.
And I suspect that if a student marched into your office and started complaining about the way a professor manages her classroom, you'd have some questions about how much, how often, and why. I also suspect that there would be a big binder of some colour or another. I don't think your first piece of advice would be to tell him to march his butt up to the deans office, file an official complaint, and demand a refund - which is what you suggested this student do.
I would be quick to help my faculty members who have trouble maintaining a civil classroom.
Help is one thing. Especially if a 70 year old, likely tenured, professor who has probably been doing this for longer than you've been alive requests your help. But demanding a professional review based on the comments of one student, who wrote his comments while admittedly still upset over not only the situation, but his own reaction to it? That's a whole other thing.
Professor has said, in essence, that nothing will change. OP is entitled to take this further if so desired.
And here we're in agreement. Thankfully, the OP did not take your advice, and decided that instead of overreacting again, he would speak to the professor herself to see what could be done. It's entirely possible - and hopefully so - that nothing need be done, now that the worst offender has dropped the course. But if that's not the case, the OP now has some idea of what his next course of action could be.