I had a good laugh reading that thread. "Despite the huge profit we earn, we are closing our activity." and then denies any pressure from anyone. 
Yes, made me lol too. The going at him hard for being a moralist.
He tries to make BTC more legally acceptable, but in the past he has been stimulating illicit activity using bitcoin by providing a mixing service. Hypocricy.
dunno ..kinda think that statement might be a way to alert people mixing really won't help if the wrong people are interested in you.
EDIT: one thing i find interesting: alphabay was renowned for utilizing mixers. so-much-so that people would complain about them bogging things down.... they were still traced via bitcoin.
On the other side of that coin, it's really super convenient that they're shutting down just before there's a possibility of BTC taking a big dump. Whether it's to be believed or not, some people have already made up their minds. This could very well be a "Well I made my money! I'm out."
The morality excuse being used is definitely a load of horse manure.