Did you feel the same way when Wikileaks was releasing Clinton's emails? I don't think Wikileaks got a warrant.I can not find anything that says that the recording of Flynn's conversation did or did not need a warrant. I do know that the intercept was considered classified information and by releasing it to the media a illegal act was done. Now you and other may think that the releasing of classified information is not a issue if it is considered "the public needs to know".; however I and others do not agree and the law does not agree. If we are a nation of laws and we only enforce the ones we "like" then we are not a nation of laws.
If Flynn did nothing wrong, why did Trump ask for his resignation? It makes no sense. Trump is trying to say that this is all about the leaks and the media. But the media didn't make Flynn resign, the democrats didn't make Flynn resign, the FBI didn't make Flynn resign. Trump asked for Flynn's resignation. Why?As far as your other comments about a potentially illegal attempt to undermine the US government suggest you read the following article.
FBI reviewed Flynn’s calls with Russian ambassador but found nothing illicit
I suggest you read the this article.
Flynn in FBI interview denied discussing sanctions with Russian ambassador