Thank you, T'Girl, for using the word that was the fulcrum of "Day of the Dove": manipulating.
The "*" alien did not place murderous violent intent in the minds of the characters by mind-control per se, but, like the Talosians, it used a combination of tricks (maybe some transmutation, maybe some illusion) to manipulate everyone into fighting.
I agree that the ending was loose, but not entirely open. We don't know what happened to the bulkheads, but we assume that the trapped Enterprise crew were freed quickly. (Even if the bulkhead metal didn't change back to normal, at least someone was able to pry the doors open.)
Kras, the Klingon agent in "Friday's Child" was not necessarily a starship officer; more of an intelligence agent. He was therefore easy to cast as sneaky and dishonorable. Kor, Koloth and Kang were clearly starship commanders, and therefore bound by the honorable "maritime rules". (See "The Enemy Below" from 1957, starring Kurt Jurgens and Robert Mitchum to see this illustrated clearly.)
When Kang and Mara finally realized the true threat was the "*" alien, they behaved in a maritime fashion, working with Kirk to save the ship. While the ending is a bit cheesy and left to the imagination, it made sense.
