The real effect of the 17th was probably just to change the location of corruption from state capitals to DC. Resistance to the repeal of the 17th does indeed also come from many conservatives who say they just don’t trust their state government! Presumably, switching corruption to a place where they don’t know as many of the players allows them to sleep better.
For a serious deeper look at the history around the 17th Amendment, here’s a lengthier treatment:
http://press.princeton.edu/chapters/s10401.pdf
It's easier to manage 50 corruptions localized to their individual states, instead of the collusion of corruption at the federal level that is nationalized.
At least with the states, you have the self-interests of the other 49 states to balance the corruption of a runaway state. National corruption ends with weaponizing the arms of government against its people in order to protect the establishment.
At the very least, doing away with the elections will dry up the existing money spigots, such as McConnell's NRSC. He will have to rebuild a new power network to replace it, since it would be harder for McConnell to use national money to influence the state appointment in Mississippi or Alabama, like he's doing now.
-PJ