The politics and science of the Dietary Guidelines have been criticized before 2015, as well:

In the face of contradictory evidence: report of the Dietary Guidelines for Americans Committee.
Nutrition (2010)
Adele Hite, School of Global Public Health, University of North Carolina at Chapel Hill, et al.

A Call For Higher Standards of Evidence for Dietary Guidelines
American Journal of Preventive Medicine (2008)
Paul Marantz, Professor, Department of Epidemiology and Population Health, Albert Einstein College of Medicine, et al.

Letter in response to the above article:

Evidence From Randomised Controlled Trials Did Not Support the Introduction of Dietary Fat Guidelines in 1977 and 1983: A Systematic Review and Meta-analysis
British OpenHeart Journal (2015)
Zoe Harcombe, obesity researcher and author

Saving US Dietary Advice From Conflicts of Interest
Food and Drug Law Journal (2010)
Herman J., Saint Louis University School of Law.

Flaws, Fallacies and Facts: Reviewing the Early History of the Lipid and Diet/Heart Hypotheses
Food and Nutrition Sciences (2014)
Jennifer Elliot, dietician.

Toward Healthful Diets
National Research Council, Food and Nutrition Board, National Academy of Sciences (1980)
This was the original report published by the National Academy of Sciences challenging the DGAs when they first came out.

The Soft Science of Dietary Fat
Science (2001)
Gary Taubes, science journalist.

 

For the 2015 Dietary Guidelines, there was an unprecedented level of concern. Read here.