@Lisan: It's equally disrespectful enough to upload doujinshi in general considering most of the ones you see uploaded daily are also available for purchase, either digitally or with varying degrees of difficulty acquiring a physical copy.
At the end of the day, E-Hentai is a wild-west sort of community/file portal, and it's totally possible for artists to have themselves blacklisted from uploading. If 3mangos gets mad at this (which he may, or may not, I THINK I saw him comment on another pack uploaded saying it was OK as long as his name was on it and people would at least consider buying it if they liked it) he can always request it be taken down. Not like I haven't seen stuff like Witchking00's disappearing galleries.
Most actual artists take gallery uploads for what they are; Free publicity and traffic which can lead to commissions, which ultimately means funds. As for manga and douginshi, remember at lot of people go out of thier way to translate them to enjoy in thier native language (since the artists sell them with the intention of them being local) or pay someone else to translate and edit the original.