I was trying to say, though, that who funded a study or an organization does not make that organization's or study's findings wrong

It doesn't make them wrong but it makes them more likely to be wrong. The effect is well established by scientific papers. There are many ways to bias a study that you can't trace by reading a paper.

It doesn't make sense to say look at the science, and ignore the science that clearly establishes that funding sources bias scientific papers.

IFIC are not in a good position to turn any money down, as long as the money doesn't dictate their message

You don't need to dictate a message to encourage an organisation to argue position that are in line with your interests if you are clear about your interest and give them money. Corruption works quite well without direct dictates.

pretty much the last thing you want to do is put the McDonalds or Pepsi logos on your front page, because it creates a confusing message

If you look at the website it's interesting to see the hoops they put up to get people to see the funding sources. The first step is to find an click the about button. There you get the paragraph:

OUR STAKEHOLDERS We bring together, work with, and provide information to consumers, health and nutrition professionals, educators, government officials, and food, beverage, and agricultural industry professionals. We have established partnerships with a wide range of credible professional organizations, government agencies, and academic institutions to advance the public understanding of key issues. For example, we have a long-standing relationship with the U.S. Department of Agriculture Center for Nutrition Policy and Promotion as part of the Dietary Guidelines Alliance, a public-private partnership focused on the U.S. Dietary Guidelines for Americans and the MyPlate Food Guidance System.

It misleading. It speaks about relationship with professional, when in fact the organisation has relationships with companies that pay the majority of it's budget.

If you want to know more, you can click "Partner and sponsors". That brings you to a black and white PDF page. There no reason avoid having normal html page that list the "Partner and sponsors" and uses the logos unless you want to design the website in a way that makes it harder for the user to find out the funding sources.

Another interesting part of the website is an article about beef. It reads like a beef commercial:

Every parent wants to feed their family safe, nutritious, and healthful foods. If you’ve seen recent news articles on grass-fed versus grain-fed meat, you’re probably left wondering how to choose what’s right to purchase for your house. The short (and pretty low stress!) answer is that whatever choice you make, either conventional or grass-fed beef or milk, is a great option for you and your family.

Of course McDonalds wants people to eat beef. In the mainstream nutrition community there a general belief that the average American eats too much red meat. Given that background saying "don't stress about the choices you make about beef consumption" is problematic.

Of course there are paleo people who think that eating red meat is quite alright, but it's still highly suspicious for the authors of the website manage to argue the position that it's funders would want it to argue. The paleo people wouldn't advocate milk as a good choice.