So if I sneak into a movie theater and watch a movie without paying, the theater can prosecute me for trespassing and/or stealing.
My question then: Can the movie rights owner also prosecute me if they wanted to?
If not, why? Wouldn’t me sneaking into a movie theater and watching a movie without paying be the same as watching the movie on my PC without paying? Where does the law come down on something like this? Or does it even come down? 
The copyright laws do not concern themselves with watching a movie (or reading a book, or listening to a piece of music, or whatever). They concern themselves with making a copy of a movie (or book, or piece of music…). The way movies on computers work, the computer must inevitably store a copy of at least part of the movie, at least temporarily, somewhere on the computer. But no extra copy is needed to watch a movie in the theater.
And the charge (in most jurisdictions) would be theft of services, not tresspassing.