it's not stealing because in most legal systems you can only steal physical objects and only if you have the intention to permanently take them from their owner. But you are incorrect that it doesn't influence anyone but yourself.
"he would see no more money if i didn't see a pirated copy of a movie for free"
You don't have the right to do decide this for yourself. If you watch it the law says you have to pay. If you don't want to watch it then you don't have to pay. Watching without paying is simply not a choice that is legally available to you (excepting legal exceptions like family showings and such of course). That you may or may not be willing to pay to watch is entirely irrelevant. The copyright holder has a right to his income as soon as you decide to watch and therefore illegal viewings cost him money he is rightfully entitled to. It's really simple. If you agree that it is illegal then it's pretty weird not to acknowledge this, you can be assured that if you're ever in court for copyright violations your argument would be laughed at and you would owe the copyright holder mucho cash.
Also the argument "omg it was soooo goooood that I decided to buy it" is really contrived, almost nobody does this (duuhhhh) and even how much of those purchases are at a reduced price rather than the high initial offering price?
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