My complaint about "gentleman" is not so much political, but general usage. Gentleman used to mean a man who was polite, educated, well-dressed, and generally a decent sort of chap. Today it seems to be used like the word "alleged" to give the benefit of the doubt to criminals, and to avoid libel suits against the news media. So, we hear them talk about a serial murderer, saying that the "gentleman" might be moved to a new prison. Part of the misuse is intentional because "gentleman" conjures up an image of a past time in which most people were much kinder and more thoughtful than they are today, So, they undermine that image by associating "gentleman" with the worst kind of things today.
A year or two ago the Republicans started referring to the Democratic Party as the Democrat Party, presumably because it has a coarser, more grating sound, but also perhaps because "Democratic" called up better images of democratic government in the Athenian tradition, than "Democrat" which in the US generally means a person who is Democratic politician or supporter. However, "Democrat" is a noun, while "Democratic" is an adjective. So, it's grammatically incorrect, but the main appeal for the Republicans is probably that it sounds harsher and thus it's easier to make "Democrat Party" sound insulting.
Finally, I don't like the term Progressive. To me the Progressive movement is something that happened in the first half of the twentieth century, limited to unions, social reform, etc. On the other hand, "liberal" is a term that again goes back to the ancient Greeks. It speaks of freedom; we have (or used to have) "liberal" education. Liberal speaks of freedom, of issues that are important to every civilization, while progressive is more economic and limited to certain mundale issues, times and places. I much prefer being a Liberal than a Progressive.
To the extent that the Democratic Party tries to make me a Progressive, rather than a Liberal, I feel less like a gentleman.