Because that's the game: e.g. Its not 'bad' or improper that Russia tries to influence American elections, its a failing of America that American elections were influenced. Countries exist to serve the citizens of that country so damn right America should tell other countries to fuck off: because they can and do so when it is (presumptively) good for Americans. (and damn right the Russians should try and influence American elections, Brexit, etc. if they feel it is in their interest)

What superficially is a hypocritical position is merely 'I do what's good for me'. Not endearing I suppose, but its not supposed to be.