If that comment was addressed to me - I was responding to an apparently non-specific statement that could be applied to almost any situation, not just the one from the question. In the case of the question, as others have found, there is no direct proof the person of the profile was a participant in that particular incident, even if the regiment to which his company belonged was. That isn't to say he wasn't involved in any massacres at all, just that proof of involvement needs to be given
In a more specific case such as "a member of a Waffen-SS unit involved in mass executions of Jews in Poland" being written up as having participated in genocide - I would have no problem with that being the language used, presuming there was evidence to back up the statement.
I have no problem - in general - with stating red is red, not orange, providing there is proof to back it up. My great-grand-grandfather was an adulterer, fathering a child with a woman not his wife, while his wife was under the same roof. His brother fathered two children "without benefit of clergy" (not adultery, as neither were married), before eventually marrying the mother of his children. More than one other of my great-grands had children before they married. My father was a serial adulterer.
I have no problem stating these as facts, because they were. On the other hand, if there were family members likely to be hurt by words (which there are), I would soften the language used, while still stating the facts.
There is no benefit in using intentionally incendiary language - words used deliberately in a way to elicit a particular response (revulsion, hatred) - when the facts can be written in a way that nothing is lost, but the reader gets to make up their own mind what response they will have.