Later Kirk escapes from them, calls a truce, gives them aid, calls them friend and sets course back for home without any mention of bringing the aliens up on charges.
You seem to forget the Kelvans still have an impressive tech edge over the Federation. I doubt the Federation could really keep them locked up if it came right down to it.
Flying Spaghetti Monster wrote:
If he hadn't done this, they would crushed the entire crew.
And, one could also say that, in the episode Kirk and his rew taught them about the vulnerabilities of humanity, and that if they had known that before, they might not have done what they did.
Sure everyone agrees that killing the female redshirt was wrong,but you can't impose consequences as normal to this race. I kind of compare it to the way Picard had no way to adequately punish Kevin Uxbridge in "The Survivors."
All this is true, but it makes for a bad statement about the value of life, particularly when they are the unknown Red Shirts.
Kirk could have told them that what they did was considered immoral and their victim deserved justice (Just to see what they would do, as they managed to get the best of them later).
In the end, it was all about the Kelvan's enjoyment and pleasure seeking. No apologies for what they've done earlier. So much for the female crew man.
'Hey, here's a nice planet, you've got human bodies, why don't you go on staying here and explore your new erotic, physical sensations together?'
You'd be surprised at the number of episodes where Red Shirts get wacked or something serious happened and later, the crew is cracking jokes like they have short term memory syndrome or something.