but more importantly, suppose it did hurt dreamcast. wmil already said that. if you're convinced that this is the correct position, why not point to interviews or news articles of the time to prove your point, instead of just endorsing someone (as if that proves anything)?
Sega and game devs weren't eager to advertise that fact, so you're not going to find any articles. But once that happened developers weren't putting money into new releases.
I remember buying a second hand PS2 for Guitar Hero. The aforementioned game was pretty much the only original game that came with it, it was also bundled with a Swap Magic disc and about 100 pirated games. Clearly pirated PS2 games weren't hard to come by. However, the PS2 was hugely successful, so from the point of view of a game publisher even if you lose a high proportion of potential sales to piracy you can still make a profit.
This article gives some insight into how important strong software sales were to the survival of the Dreamcast:
http://www.polygon.com/2013/8/7/4599588/why-did-the-dreamcas...
Whilst the Dreamcast did not have the worst ever attach rate, any downturn in sales was not something sustainable. As I said in a different comment, if the Dreamcast had been released with a DVD drive (even if this bumped up the retail price) then this would have helped immensely, not only to counteract piracy (DVD burners were much rarer at the time), but also to take away one of the big reasons for waiting for a PS2. Whether they could've afforded to do so in 1998 is another matter.
How many developers abandoned Sony because of that?
Konami, EA, Squaresoft, etc - all these developers had already decided they wouldn't have anything to do with the Dreamcast before it launched. Had nothing to do with the piracy scene that cropped up a year or so after the DC launched.