You have totally, abominably misunderstood the film.
And since you're going to come back with a disagreement, I'll explain to you why.
Firstly, artistically. The whole film was shot in 13 long takes and most of the dialogue is improvised. The actors worked without a script only being told what to generally say. That, in itself, is a great feat. This was director Noe's second ever full-length film and gained him numerous awards and nominations.
Second, morally. Being told back to front, the film forces us to think about the consequences of our actions before we see the causes, and whether the outcome is justified by the violence. Of course, it very rarely - if ever - is. There is an ethical point to the backwards theme, rather than just a plot-based one, such as in Memento.
The violence is, in itself, sickening - and this is exactly Noe's point. We have become so desensitised to violence through the media that many of us have seen possibly thousands of acted-out killing and deaths, and most of the time we feel nothing when we see them. Noe's depiction of violence makes us feel disgusted as we should when we see someone getting beaten up, or getting raped. It reminds us of our true feelings towards these things when they're not being glossed over by Hollywood and the big studios. They're vile, they're despicable, just how they're shown in the film.
By giving us insight into the characters' lives - before and after the events - it shows us how atrocious violent acts really are and how they can destroy people. They are Irreversible, you can't change them afterwards, and they can destroy peoples' lives forever. The moral at the end - "Time Destroys Everything" - posits time as the ultimate destructive force. In the end we will all come to nothing, and we should make something positive of ourselves on the way. The choice is ours.
