Even if our politicians are so corrupt that every one has skeletons in their closet, I don't think releasing factual evidence of malfeasance is a type of election interference that should be condemned.
there are examples of files and tapes which veracity isn't in question in a much bigger and more important country than Slovenia regarding much more important people than the Slovenian prime minister and... it doesn't matter much, apparently
The candidate who stands to benefit from circumstances like this is usually quite corrupt as well. The mere appearance of a foreign espionage outfit helping one candidate should raise questions about their integrity.
Sausage is made by all parties. If you show how one party makes its sausage, and only that party, that is a smear campaign a foreign power must not assist in. Same as donating to one party, it is interfering with electuons