The "evil" of software piracy is very simple: Someone has built a program, and you copy it and enjoy it without compensating them.
It is pretty much indefensible, except maybe by people who like it when someone swoops in on their jobs and takes the result of their efforts without paying.
I personally think the big problem with software piracy is how the industry sees it. The usual argument is that DRM is necessary because if piracy was impossible, all those pirates would end up buying the games (or movies, or musics...). I think it is the other way around. I think it is the ease of piracy which has resulted in the self-entitlement attitude so many people have regarding software, and if those people couldn't pirate the content easily, most wouldn't bother, because, in the end, they just don't really care for the content, they only care it is easy to come by.
Or, in other words, the percentage of pirates who would turn into customers is probably very small. The point then is to evaluate if the hassle (to producers and legit consumers) of DRM is worth that tiny increase in sales.
The bottom line is that the audience for a given piece of entertainment is not the sum of legit plus
pirate users, but rather just the legit users
(Who care enough to actually buy the product), and it is those who should be the focus of the developers.
Of course, this is just my opinion based on my observations (Like how Ubisoft's always-on DRM didn't make Assasin's Creed 2 sales soar, despite it remaining uncracked during the launch period... In fact they were worse).
As for using non-paying customers for profit, freemium games do that. F2P MMOs benefit from freeloaders because they create a community, which is an essential element for that sort of game, and, in general, free-to-play games get the chance to market to users and try to sell them stuff.
Of course the dark side of freemium games are the digital-beggars, games designed to have the player pay constantly to progress in the game (See: EA's Facebook games).