Is David Shuster a bit of a smarmy ass at times? Sure.
Was he actually trying to imply that Chelsea Clinton is turning tricks? No.
He's pointing out there being something weird about the way the Clintons are handling their daughter to further their campaign. They generally won't let her be interviewed. They tried to shelter her early and often before Hillary's run. Now, they have her calling super-delegates at their express behest, but won't grant requests for interviews to the media.
There is something off about that. There is something weird about it. There is, certainly, some manner of using going on there...and even, possibly, creating an artificial demand for her by trying to control who can and can't hear her speak.
And the idea that MSNBC is in the hip pocket of the Obama campaign? Ridiculous. Months ago, Olbermann practically fellated Bill Clinton on a regular basis and was a Hillary apologist any time something popped up. I'd say the first time he started being objective when it came to her campaign was when he was the only on-air personality there to point to the fact that she didn't skip a beat after crying in New Hampshire to launching into an attack on Obama. He alluded to it appearing to be calculated, while no one else working on their primary coverage seemed to even acknowledge the possibility.
The Clinton campaign thinks that any reporting of their work that doesn't read directly off the script they provide to the media is biased and out to get them.