Sanders fired back by going on a tear about how special interests buy off politicians all the time. Clinton said that no one has been more targeted by those special interests than her.I don't see why anyone on the left should be complaining as Jimmy Carter has endorsed Don Trump as being more amenable to compromising his positions. For him, this is a selling point.
The old saw about an honest politician being one who, once bought stays bought is really only applicable to places like Chicago or New Jersey where being bought by the local mob had darn well better mean staying bought. On Wall St the interpretation is a bit different as financial types don't normally have kneecappers on the payroll or even the speed dial.
In the better parts of town you don't buy politicians. You rent them, by the issue.