the movie was essentially a satire of the themes espoused by the novel - i think it was a brilliant way of subverting Heinlein's views through an 'adaptation'. it could have been more consistent with that theme for sure, but i'm surprised by the number of people who hadn't picked up on that.
from imdb - this comment sums it up:
The film is insanely violent. People are literally cut to pieces by the smaller creatures and slowly, painfully melted by a plasma the larger insects spray. However, the alien bugs fair no better. The people and cows getting hacked up relentlessly in this film horrify us but we cheer as machine rifles and grenades blow the giant insects apart. The body count is high on both sides. It is all literally and purposely utter, senseless violence. But then at one point a psychic uses his powers to read one of the alien's emotions. He triumphantly yells, `It's afraid!' and a legion of human warriors jubilantly cheer at this pronouncement. Who's barbaric here? What is humanity? These bugs are clearly not `human' yet they are intelligent, advanced, and most importantly they have feelings. If they can be afraid, can they not also be sad, happy, in love? These are questions the writer has left to us to ask with out leading us by the hand through what could have been a much more preachy film.
Considering the fact that, in his book _Stranger in a Strange Land_, Robert A. Heinlein--who wrote the novel upon which Starship Troopers was based--pointed out that there were millions of people already in America before the Europeans came and ruthlessly slaughtered these `subhumans' on their new property, it is safe to say that there is a lot more going on in this film than a simple slug-fest. The dazzling special effects and heart pounding action are all just a distraction--like all the noise in real life--from the more important things said here. Even the trailer and commercials for this movie were purposely misleading with Blur's delightfully mindless `Song #3' blaring and the singer yelling `Whoo-hoo!' as a stream of soldiers pour out of ships to go to battle. Every aspect of the film was one gigantic, satirical slap in the face of humanity and no one noticed.
Some may suggest that the satire was not intended but that would be incredibly insulting to screenwriter Edward Neumeier because that's what he excels at. If you didn't catch the not so subtle satire in his earlier screenplay for _Robocop_ then you're under the age of ten. Despite being so financially successful, _Starship Troopers_ is one of the most important, yet overlooked, movies of the 1990s from an intellectual point of view.