Objectively unethical, subjectively criminal activity. In 2016, it was unregulated software code during a "code is law" mentality. The regulatory agencies hadn't caught up (the IRS had laid claim in 2014 then revised in 2019).
Yes, similar reasons would justify taking your fiat away. I do sympathize with the Ethereum Classic crowd and generally agree with the code is law idea. The investors very well knew the risks.
Hacking the DAO was objectively criminal activity, since it was illegal.
Ethereum agreed to fork to within a margin of error. I know this because the post-fork version of Ethereum is much bigger.