To be honest, I can also understand the opposing viewpoint - that by buying DRM-ed software (even if you pirate it afterwards to remove the DRM features) you basically tell the publisher that you are fine with their DRM. Eventually pirating your legally bought software might not be a viable option anymore (due to various online-only features, for example), most/all of the software companies will have switched to DRM, since it works - see above, and THEN you'd have no recourse but to use DRM-ed software.
That being said, once you've decided not to support the publisher because of their DRM, you might say that pirating it doesn't harm them, since you wouldn't have paid for it anyway. Personally, I think it really doesn't harm them and what's more, on average it actually helps them a bit - by using even just a pirated version, you are still helping them expand their user base, which helps them also get more paying customers. As a really simple and probably exaggerated example, let's say Company X sells 10.000 copies of their software, while 100.000 more people just go and pirate it. 10% of all users then go and post on an online forum about that software. That means 100 paying customers and 10.000 pirates. Now Joe Average hears from someone (maybe even a pirate) about the software and goes to Google to see what it's about. He finds a forum with 100 legitimate users and thinks - "meh, nobody ever uses that thing - if I ever need help or suggestions, probably nobody will be around to help me, so I'll buy the software from Company Y instead". If he finds a forum with 10.100 users instead, he might think - "hmm, that seems like a big and active community, looks like that's the right software for me".
So, if you are 100% sure you won't pay for some software and want to demonstrate to the company that they are wrong, you shouldn't even pirate it, because by doing that you are still helping their bottom line at worst, or aren't making any change at best (because they can't know you've pirated it instead of simply not using it).