Would you feel the same if it was the Chinese or Russian government who wanted to prosecute a foreigner for allegedly helping one of their whistleblowers, or for just criticizing their government? Unless you want Americans sent to Beijing for violating the Hong Kong national security law, which applies to everyone in the world according to the Chinese government, I don't see how you can invoke 'the law' against Assange.
Regardless, laws are completely irrelevant to what's right or wrong. Laws are basically just threats, and it's not wrong to do something just because someone threatens to harm you. It doesn't matter if that someone is the Chinese government, the US government, the Taliban government, or some local street gang.
I think they meant that if anyone had the power to protect people's rights, they would also have the power to violate people's rights, and they would use that power in the same way as today's rights violators. If so, I think they are absolutely right on that point, and it holds true regardless of what you believe those rights are.
I certainly think some things are inherently wrong, but doing those things are not any more difficult than doing other things, and it's probably easier to do them than it is to prevent them. We can't rely on an organization or institution to protect us because any such group will always promote and protect each other first. Instead, we need to promote a culture of direct action on an individual level, praise and encourage whistleblowers, activists, saboteurs and others who do what they think is right to weaken the power of institutions over individuals. We won't always agree with their goals, judgement, and morals, but as long as they don't use methods that are unequivocally wrong (such as violence against non-violent people), we should support them because individual action is in aggregate much better (and much less dangerous) than institutional actions.
I mostly feel contempt for the mainstream media nowdays, but that does nothing to diminish my support for their right to freedom of speech. Freedom of speech is most important for those whose speech we think is harmful and don't want to be spoken. Nothing would be more dangerous than letting those with the greatest capacity for and willingness to use violence (e.g. governments) decide what speech should be allowed.
Anyone who cares about freedom of speech for anyone should defend it for everyone because if nazis, tankies, and journalists can't have freedom of speech, none of us can. First they came for... you know how the rest goes.
Regardless, laws are completely irrelevant to what's right or wrong. Laws are basically just threats, and it's not wrong to do something just because someone threatens to harm you. It doesn't matter if that someone is the Chinese government, the US government, the Taliban government, or some local street gang.