I'm not a fan of disinformation. What if a letter of a similar nature had been written to the chairmen of major tobacco companies about 30-40 years ago, asking them to cease funding of "agents" (for lack of a better term) that kept putting out information questioning the link between smoking and cancer (which was not "proven" at the time)? Would you have objected to that?
Absolutely. Let the senators combat rhetoric with better rhetoric in the battle for public opinion. (Although in the case of tobacco, I hesitate to endorse any Congressional intervention at all).
If they have to threaten government action to "win" an argument, they've already lost. Or rather, we all lose in the general dumbing down.
If AGW constitutes a serious enough threat to the general welfare, Congress should act. But it doesn't need censorship to aid its deliberations.