It is important to remember that stealing is really just taking what is not freely given. In other words, if you didn’t pay for it, and the owner didn’t say, “here take this, no charge”. Then possibly you are stealing it. There is a large amount of content on the internet that appears to be free but really has already been stolen and you viewing it is also stealing.
Sometimes it is hard to tell as you look at a list of movies on a site like Hulu and realize that all these movies are available for you to legally view. And then there are other sites that have a list of movies and this is actually pirated and it is not legally available for you to view. How does one know the difference? Honestly, it can be tough, but it is up to you to tell the difference. Generally you can tell some differences between legal sites and those that have pirated copies available for download or streaming. One sign might be just the quality of the site overall.
The hard part is that it doesn’t always feel like stealing. You don’t really keep anything and after you watch the show it seems like there has been no harm done to anyone. The fact is though, that in the United States, this is considered theft. You are probably putting money in the pockets of the thief by viewing the movie on their site instead of in the pocket of the people that produced and created the show.