A good thesis statement for this idea would depend on what point you are trying to make. There is more than one reason why a person might support the idea of illegal downloading. Here are some possible thesis statements.
- The process that we often call “illegal downloading” should not be illegal at all because it disseminates knowledge and ideas more freely across the world.
- Illegal downloading is only illegal because the music and movie companies of the world want to make an unreasonable profit.
- Illegal downloading should be a right because everyone who has bought a movie, song, or other piece of software should be able to share their property as they wish.
- Illegal downloading should be encouraged instead of banned because it can actually be good for the artists whose music is downloaded.
Any of these would allow you to argue that illegal downloading should not be illegal and that, instead, it is something that is positively good.