it all happened so fast. click on a genre in the top pane and all the artists in the genre appear in the bottom pane...then right-click on an artist on the right-hand side of the top pane and select "delete"...and "poof" all the artists in the genre are deleted because that is what is showing in the bottom pane.
I just tried it for "fun." I had the tracts for artist "A" showing in the bottom pane. In the top pane, I highlighted artist "B" and deleted artist B via right-clicking. Unfortunately, artist A was deleted instead, because that's what was showing in the bottom pane at the time. Sure, the dialog popped up asking if I wanted to delete the tracks. and, I said yes because I did want to delete the artist that I had selected in the top pane. unfortunately, what was highlighted and clicked on was not what the program deleted. the dialog box doesn't indicate what is being deleted, just how many items.
Another variation is to select an artist in the top pane, so that all the artist's tracks are showing below. Select one album in the top pane and delete the one album. you will lose all the tracks by the artist because that is what is showing below. the dialog asks if you are sure that you want to delete the tracks, and you say "of course I do--I just right-clicked and selected delete didn't I?" unfortunately, stupidly, one may have forgotten that the one album you selected for deletion only had 18 tracks and the dialog box asks you whether you are sure that you want to delete 95 tracks. it's best to pay strict attention to that number for the time being.