Firstly, why did Steemit.com delete the account (from their website access, not from the blockchain) ?

Steemit.com does not own the Steem blockchain. Steemit.com is owned by Steemit Inc which is owned and run by a US citizen (it's a US company). Steemit Inc as expected will be required to comply with US law. In my opinion Steemit Inc did the correct and appropriate actions according to the law.

Morally speaking I also think Steemit Inc did the correct and appropriate thing. Just because some outlaws release some information it does not mean those outlaws are doing it with good intentions or that those outlaws care about the US citizen, or any citizens in the world, or the people. Just because some outlaws release some information it does not mean the information they release is saving lives, or improving lives, or helping people in some way.

Blackmail, extortion, terrorism, are against the law. Also it must be noted that these are not victimless crimes. There are victims. The information being released was not just about 911 either. The hackers releasing it did it for profit, for money, and not for any moral ideal or higher ideal.

Of course that is just my opinion. Some will say my opinion is correct while others will say the hackers are defending free speech. I think free speech or political speech is what people like Jordan Peterson are doing (not saying I agree with his speech but he has a right). I think if you make threats, demand payment (or else), and release information which destroys lives? It becomes no longer a matter of political speech as now there are victims of that speech.

Morally I don't see these as being the same category.