I'm re-watching the movie version of ST with RiffTrax and I had forgotten this (relatively) subtle plot point. The Feds are invading their homes based on information given to us by some quasi-1984ish government. Buenos Aires' destruction is attributed to the Bugs but the source is extremely unreliable to say the least. I mean, I guess Rico isn't such a bad guy but he's fighting for a bad country.
Okay, maybe "good guys" was the wrong term. Consider it kinda like Rooting For The Empire but intentional. The Mobile Infantry and the government it fights for is Not A Good Thing. I think we can all agree that the movie had that message. As such, the bugs killing them and defending themselves is Not A Bad Thing.
That's all I was trying to get at.
Furthermore, didn't the whole thing start when humans landed on one of their planets and tried to take it over?
Also I wanna read the book now. But it's apparently so different that I don't think it has any bearing on this.