There is a big, politically staged fuss in California over the issue of research funded by tobacco companies. InsideHigherEd has the story.
The opponents of the proposed ban are, I think, on solid ground with their “slippery slope” argument, but there’s a better one yet. In logic, the claim that an argument should be rejected not on its own merits but just because of some feature of the person making the argument is called the ad hominem circumstantial fallacy. If, for example, person X argues that rent control is a harmful policy and someone else says, “You shouldn’t listen to X — he owns some apartment buildings and would profit from the abolition of rent control,” that’s the ad hominem circumstantial.
Same thing here. If a professor’s research calls into question the harmfulness of second hand smoke, e.g., that research should be evaluated on its own merits. Where the funding came from has no logical bearing on the merits.