Claim: refusing to help when you can do so without cost to yourself is the same as hurting. Basis: conscience. If you saw someone being electrocuted and another person standing by the power switch doing nothing, wouldn't your conscience tell you to feel the same toward the second person as you would toward a murderer? That's all the argument I'll bother giving. I will, however, talk about the ramifications.
My favorite consequence is that this removes the right of land owners to kick others off their land for no reason. This consequence may seem instinctively repulsive to you. Therefore, I'll give another intuitive reason why you should reconsider. Suppose you live in a small circle of land, less than an acre, and all the rest of the world is 'owned' by other people, so you can't leave your area. You are therefore in prison, are you not? Where do the landowners get the right to keep you there? Even if imprisonment were a valid punishment (it's not), you aren't a criminal. Does your conscience really tell you that you wouldn't have the right to trespass?More generally speaking, there is - or seems to be - the implication that freeloading is perfectly fine, and not only that, but that attempting to prevent freeloading is not fine. This is not entirely true. There are other relevant ideas that we need to consider in those cases.
First, we need to talk a little about debt. Debt is owed to someone who has made a sacrifice to help you. You do not owe someone who helps you at no cost to themselves (such as a god with infinite power). By the same token, it doesn't count as your repayment if you help the person back at no cost to you - only when you make a sacrifice for them. Another principle is that you can never owe repayment past the point where your sacrifice is equal to the benefit you gained, even if their sacrifice hasn't been fully made up yet.
So say someone puts time, money and effort into creating a video game and makes it available for purchase. The sacrifice made to create the work is now a sunk cost so it would seem that preventing players from downloading it for free is immoral by the above principle. However, debt is involved here. If you play and enjoy the game, then they made a sacrifice that benefits you, and so you should pay the minimum of the requested price and the game's worth to you. If a game costs $10 and you'd rather spend that money than not play it, then you should pay. If it doesn't matter to you that much, you'll just go play a different game if you don't end up buying this one, then it's moral to "steal" it in a way that doesn't hurt the creator at all.
One last thing. Since the above answer leaves the decision to the player who is incentivized to steal things they'd be willing to pay for, throwing obstacles in the way of freeloaders actually is moral, despite that freeloading is too in some cases. Because there's no way to discriminate, and if you let everyone freeload without any obstacles, many people who would (and therefore should) pay are going to do that instead. That means making freeloading difficult for everyone is acceptable, because it prevents theft. (This can result in a moral conflict of sorts as a benevolent freeloader and a benevolent creator's technical expertise are pitted against each other. But this should never go as far as actual violence or theft of anything other than the product in question, because the freeloader's legitimacy is predicated on not hurting the creator at all.)
Intellectual property is just another application of this same principle. Using someone's IP without paying for it is freeloading and should be treated the same way.