I kind of have to jump in on this,... In battle if you defeat an amies leadership, you defeat the army. This is a normal part of military strategy, cut off the head. Intentional or not, it only seems logical that settler combat should be the same way. If you defeat the leader, the rest of his units lay down their arms. Which is exactly what blocking is all about, getting to and defeating the leader quickly enough to avoid massive casualties.
How do people have a problem with this?