You could remove the profile's access to the mkto apex classes and visualforce page access. This would prevent them from seeing the sales insight panel but remember that you have already added the VF section to the page layout then they will see an error message :
Content cannot be displayed: You do not have sufficient privileges to access the page
Thanks Cathal, may be we can try using code to hide the error message. But again, can we successfully install the MSI application without making any changes to the different objects pagelayout? And make use of the Marketo tab primarily.