Septimus is a soldier and as long as the fight is going on, his first instinct will be 'kill.' However, once that fight's done, he'll be easy to get to listen to reason on the subject. Also, he can take a hit. As such, I am volunteering him to get punched but then legitimately listen and ultimately side with Diana--especially as he is not cool with anyone who wants to kill Kal trying to kill other teammates to do it.

This is the best way for them to meet, really. :D