These aliens were jerks of the first order to kill those people, then only demonstrated they hadn't learned ANYTHING resembling morality from it by forcing those memories on everyone who passes by.
Janeway proves she's pretty much a tyrant by supporting the mind rape of random passer bys, not only supporting it but aiding and abetting it by fixing the damn thing to make it violate people even better! And Neelix... well by supporting randomly mindraping people as if that's some great lession, this is yet another reason he's a jerk. The rest of the crew told Janeway how stupid this was, she just said screw you and couldn't pass up on the oppurtunity to make people suffer in the name of righteousness.
Thank you, I don't need to have the memory of killing someone to know that it's wrong. What sort of stupid premise is this? I'm going to violate someone to teach them morality! Yeah... stupid.