Stop talking about the Logan Act.

It was not the violation of this antique and ignored piece of anti-Jacobin legislation that has touched off the biggest foreign-policy scandal since Watergate.

...

Nobody would care if an incoming national security adviser had confidential conversations with an ambassador of a hostile foreign government before Inauguration Day, if it were believed that the conversations served a legitimate and disinterested public purpose.

But that is exactly what is doubted in this case.

To put the story in simplest terms:

1) Russian spies hacked Democratic Party communications in order to help elect Donald Trump.

2) Donald Trump welcomed the help, used it, publicly solicited more of it—and was then elected president of the United States.

3) President Obama sanctioned Russia for its pro-Trump espionage.

4) While Russia considered its response, its ambassador spoke with the national security adviser-designate about the sanctions

5) The adviser, Flynn, reportedly asked Russia not to overreact, signaling that the new administration would review the sanctions; Russia did not respond.

6) As president-elect and then president, Donald Trump has indicated that he seeks to lift precisely those sanctions caused by Russia’s espionage work on his behalf.

https://www.theatlantic.com/politics/archive/2017/02/the-deeper-concern-behind-mike-flynns-resignation/516630/