Nobody said anything about HRT "ruining" careers(although I do think they're capable of it, and neither Senna nor Chandhok have been helped on their way by their 2010 drives), my point was that it's highly likely to be a detrimental environment for a rookie, because in that particular car and team it's questionable that
any driver can show their potential, since they're not getting proper equipment to drive, and drivers are getting casually dumped out of the team as and when it suits Kolles, so it's not exactly conducive to driver confidence. It can't not be a risky move for a driver just entering F1. Ricciardo is a bit different, because he has RedBull behind him obviously, but it's still going to be a character-building start for him.
Stars
can shine in the depths, yes, but HRT are a bit worse than just being in the depths. Of all the back of the grid F1 teams I can think of off the top of my head, both in terms of on-track performance and team management, only Life were clearly worse.