The rest of Seoul's transportation infrastructure is so well managed and universally liked that the problems with Line 9, taken in that context, make it look hysterically bad. I have to say that the labour issues sound awful, but as someone from the UK, the profiteering and overcrowding issues sound quaint and almost laughable. There's no doubt that this ownership structure was setup as a grift for juicing citizens. But from the perspective of a user, I would describe line9 as "more overcrowded at rush hour than the other lines" but on the flipside, the rolling stock and stations are newer and nicer...
The proposed price hikes were a scandal at the time and public outrage was tangible. But the relevant context here is that the Mayor of Seoul is second only to the president, and usually it is someone with aspirations to run for president. There's things a Seoul Mayor a cannot do if he likes votes, and one of those is piss off everyone who uses the metro (which is everyone).
I think with privatisation, it just depends on the specifics. If the system can be privatised without bilking the ridership, compromising safety, or abusing the employees then, by all means, have at it. But if you're writing from the US, or the UK, especially if you work within the transportation system, it's understandable that you would get ranty when you consider how badly privatisation has fucked things up there.