Hey now, I'm not part of ServerHound. I have some grievances with them, however - this was not one of them. Let's just clear that up right now. ;)
I do agree with the whole PR of this being fiasco. The way it was handled by SV wasn't really the best he could've. However, he isn't required to allow opt-outs, seeing as the data collected is necessary to the intended function of the application.
Also, the only thing that was stored by SH as far as I'm aware was the ID of the user, and the IDs of the server that they were banned in. The server name, logo, user name, guild memberships, and user avatar, were all retrieved in real-time. The Discord developers have clarified on numerous occasions that user IDs do not count as EUD. So - never mind the argument about not requiring opt-outs, but there's also a question of if any EUD was even stored at all.