Accessing computing resources that you know you aren't authorized to is a crime in most countries now, US included.
Of course, millions of things are now crimes, so just that something is a crime doesn't automatically mean it's immoral.
That said, the poster
1) Read emails that he knew belonged to someone else, a fragrant violation privacy. Do we like other people, including government agents, reading our emails? Hell no!
2) Sent messages as if they came from someone else. Worse, he sent political messages. This is even worse. How would you like it if someone used your email to espouse views you don't agree with?
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