Language is a tool.

FiveThirtyEight.com: Politics Done Right: “Democrat Party" Decrier Rips Admin for “Childish” Limbaugh Strategy:

"Musing out loud, if a critical building block in the Republican ideological persuasion strategy is first to argue that the media has a liberal bias, and media insists out of accuracy in using “Democratic” while actual Republican officeholders Mitch McConnell, Eric Cantor, George Bush, et. al. use “Democrat,” then perhaps it subtly seems like the media is taking sides by choosing the correct term. Thus, the 'liberal media' charge in turn has more merit, and that premise is critical in Republican argument given all the decades of incredible energy dedicated to that claim."