So the idea that Sanders should only stay in the contest if he respects some omertà-like code of silence is ludicrous. His critique of corruption and political influence is as much at the heart of his campaign as his concerns about poverty and inequality. Thank God someone in the Democratic Party takes it seriously enough not to give Clinton a pass.
It's one thing talking about corruption in politics in general and another pushing specious arguments about Clinton taking money from Big Oil, implying that she is beholden to them.
Sanders himself has accepted money from fossil fuel employees.
Sanders also conveniently forgets that 97% of fossil fuel industries contributions have gone to Republicans, showing how ridiculous is his attempt to convince the voters that Hillary is somehow a darling of them.
In the case of energy policy, I'm less concerned by Greenpeaces shouts of "follow the money!" than I am by concrete policy differences, such as Clinton's equivocating with regard to a federal ban on hydraulic fracturing.* I think that this this piece from Vox mostly gets it right, although it is overly dismissive of the importance of direct contributions to the Clinton campaign from lobbyists and the $3M that her SuperPAC has raised from people who are "connected with" the fossil fuel industry.
*Cue "b-b-b-but what about the jobs!" concern trolling from people who could live the remainder of their adult lives without going within one hundred miles of a fracking well if they wanted to.
It's one thing for Sanders to attack Clinton on fracking or because her Wall Street plan doesn't go far enough. It's a totally different thing for him to attack her for being a corrupt shill who has been bribed by oil/gas companies and the financial industry into doing their bidding
without any evidence and then feign that he's running a positive, issues-based campaign.