I wouldn't say they're pissed, Its just people scanlate as a hobby. And if a group has been doing a series for a long time, obviously they enjoy the series and Editing it. if its been going on for a while they've potentially put hundreds of hours into getting the series out to the readers. The harsh truth about Edited Manga is that if you don't release first, 99% of people won't read your release. So when another group picks up a series you've put so much effort into for no real reason and starts releasing faster just because they can, you can't just expect those people to take it lying down and stop working on the series. Of course picking up something other people are already doing a good job of and have been doing for ages is going to cause sparks to fly. Its disrespectful, although no one seems to care for that. If they want to do the series so badly, they should help rather than compete...