Rebuttal?  Easily done:

Campaign with him but don't fundraise with him.  Ta-da!

Not hard at all.

Alternatively:  Cleland de-lists himself as a Federal lobbyist.

If the Obama camp is going to set out its principles it would be dishonest not to follow them.  Had his people allowed Cleland to attend a fundraiser it would have been decried as hypocritical.

Those decrying it would have been right.  No lobbyists means no lobbyists not just "no lobbyists I don't like."