what a great relationship we have with our allies if we can't even share crucial information about our enemies with people that are fighting them
if the Russian relationship extends as far as us sharing information about our common enemies then I have absolutely no qualms with that and neither should anybody else really
the point is, if someone confides in you to keep information between you and them, and then you tell someone else that information, it's going to make them and other people trust you less. there was an agreement between two parties to keep something secret and it was broken, and that is going to have an effect on how well people trust our word. the nature of the information and the parties receiving it is (mostly) irrelevant here, it's just the principle of what happened that is going to turn heads.
i don't want to overplay anything here, i seriously don't think this is any kind of national security issue, but it's definitely more than nothing, and it will almost certainly have negative effects on our international reputation in the short term
