If you are not using the standard Marketo unsubscribe functionality then in the smartlist tab of the report you can add filters to eliminate people who have unsubscribed. For example, the way our unsubscibe function is set up, I add "data value changed" and then the constraint new value is false. The only problem with this is, it will remove all people who unsubscribed from the entire report. Not just the clicks column. I keep two reports, one that removes unsubscribes and one that does not.