The secession - I find it credible, if not at all complimentary for the andorians:
The andorians put the 'hurt back' mentality above what was best for their future, the future of their children.
You mentioned human irrationality - while it is understandable for one human in extreme circumstances, it is less excusable for leaders whose job is not to fall prey to their reptilian brain, but to make the best decisions for their people; or for billions of humans at the same time - indicating that most humans lack the ability to see beyond their emotional turmoil, the next minute. Many - most - humans withstand really REALLY bad days without turning into irrational berserkers, lashing out.
What followed is utterly incoherent, though - and a treason of former andorian values:
Take the cardboard andorian villains from the current book - do I really need to expand on this?:
-the totalitarian laws against not-at-home andorians;
And that 'racism' conclusion an andorian reached in the DS9 terrorist incident - if that's a valid conclusion, then a person who failed to say 'good day' to me is racist towards me - and, of course, as such, deserves to die. It was established the andorian had orders/help from his homeworld - without further clarification; quite possibly, from a legitimate andorian ruling body.
The mind-control revelation turned the andorians from utterly incoherent to pathetic - frankly, any species who is so easily controlled by a foe NOT technologically - or in any other obvious field - superior will not survive in the long term regardless of its reproductive prowess.
In my opinion, this is somewhat of a promotion - especially with the mitigating circumstances to be introduced.