The voice over puts this on "Mormon Extremist Settlers", yes.

The problems with that is:

1. Those are still humans settling in bug space
2. Can we believe the propaganda voice over?
3. Mormon extremists?

The propaganda machinery of the Federation would never take responsibility, it's all about keeping the populace in a constant state of fear, anger and hyperpatriotic, unthinking loyalty. We keep hearing about the "Arachnid exclusion zone" and "quarantined bug space" which implies that the Federation has been trying to restrict the bugs from leaving their space, while the map of the galaxy, showing where earth is and where bug space is located makes it pretty clear that the Federation of Citizens has expanded aaaaaaall the way across the galaxy. Knowing how imperialist settler colonialism works, it's easy to see how the Federation is either

a) sending settlers into bug space to expand their own territory, or
b) engineering conflict with the bugs in order to keep the militarist machinery rolling, or
c) most likely, doing both.