If it's one individual, you can look up that person in Marketo and use the flow action "Remove from Flow" to have them removed from the smart campaign. You can then remove them from the program if they are a member. It will take a few minutes for them to be removed from the SFDC Campaign if you have one synced. I use the SFDC Campaigns to determine which campaigns/programs people are members of in Marketo, particularly for nurtures that are triggered from Sales Insight. You can see the campaign history in a lead or contact record.
