Well strictly speaking, before the internet came about, to watch a movie, one had to either go to a friend’s house to watch it, or the movies or buy the movie themselves.
In the first case, someone has bought the movie, and viewing a movie at someone else’s home is considered private use, which is acceptably by copyright laws. The movie cinemas has a licence to playback films for payment, if you buy the movie, you have the right for private home use.
When it is on the internet, due to someone uploading it, and that someone doesn’t have copyright holdings of the movie or permission, he starts to give it freely around to others, who has not purchased it. The case against this by p2pers is that everyone is a ‘friend’ and the concept is similar to someone coming to your house and watching it. Which is of course rubbish. Upload something onto youtube and of the 100,000 that view it, how many exactly do you know? Probably none.
Eitherways COPYRIGHT claims that distributing it without their permission IS violation, and obviously if you do not buy the movie, but watch it online due to someone else uploading it, the point is, you have not paid for watching it, it is similar to going and shoplifting from the local DVD store.
Movie publishers expect payment, and how else would they be making money if people are uploading and letting everyone else watch it without payment? Whether they are greedy or not is not the point, the commandment thou shalt not steal applies here. Render to them what is theirs.
Whether you download the movie onto your computer or just watch it, the end result is the same, you viewed it without paying. I am not condemning anyone, I have done this for years, but recently I got rid of 1400 songs that I did not pay for. And pretty much all the movies and games I did not buy, I still have more to get rid of because I have a lot of pirated stuff from the years.