Why does Engage hate a good Field Merge?

Overview: We have built out email templates for our sales team to use in Engage. Each template includes an introduction with a Field Merge for a FirstName. Some sales reps. do not have a first name for their contact and would like to delete the field merge and send the email without a first name. When we built our templates we left the introduction section of the email un-protected so they could delete the Field Merge if need. But...

Issue: When you delete the Field Merge and try sending the email the contact remains orange in the address bar and the contact record for that specific contact pops up just like it does if the Field Merge was still present in the email. Our sales reps. do not have permission to edit contact records, not to mention there is nothing to update since the rep. does not have a first name to enter.