This chapter really sells it for me - I think it provides a much more insightful perspective on the series of events that occurred over the past chapters.
The whole massacre really came about due to an unfortunate series of events + misunderstandings - first the burning of the web, then Kumoko appearing at the wrong moment, misjudging their strength + intentions, and things just went downhill from there due to the inability for both sides to communicate with each other.
Had Kumoko been in her nest slightly earlier, she might've noticed and freed the trapped soldier herself with thread manipulation; if the group had left earlier, the soldiers might have not immediately attacked her, and she wouldn't have retaliated, nor realise that humans gave a lot of XP. Without communication, the humans also couldn't tell Kumoko that her thread was so strong they had to use a massive fire spell, nor that people actually wanted to establish friendly(-ish?) relations with her.
The situation's a bit like trying to appease a dragon, where the slightest misstep could cost lives - while I think Kumoko definitely acted ruthlessly (from a human perspective), the tense situation and bad coincidences really didn't help either - and given what she had to go through previously in her 'eat or be eaten' world, her actions definitely make sense to me. Things done in the heat of the moment are generally not representative of one's entire mentality.