Donald Trump has called Mexican immigrants rapists and murderers. He has called for a ban on all Muslims from entering the country and thrown suspicion upon all of them who are already here including those who are citizens. He attacked a family who lost a son at war for the US. He has a long history of racial discrimination going back to the 1970s and has nearly 0% support from blacks nationally. The litany of horrors that has done and has spilled from his maw goes on and on. Yet it is his 11 year old hot mic pre-interview gibberish with Billy Bush -- where Trump brags about how he attempted to bed a married woman, talks about her as merely a sex object, then continues on to do the same about a woman about to bring him to a soap opera set for a cameo, while explaining that as a "star" he can get away with doing anything to women, including just walking up and grabbing them "by the pussy"-- that finally has his own party in an uproar. This doesn't even touch on his "policies" of kowtowing to Russia, encouraging nuclear proliferation, instigating worldwide trade wars, and further rigging the tax code to favor the filthy rich over middle class Americans.
Since Trump has already defined himself as a caricature of a human circa 1955, why is this interview such a big deal?
People of conservative bent have a tendency to think of the world and politics purely in terms of their own familiarity; the words they want to hear, the people they already know, the ideas that came before them.
All of the other statements that have shaken Democrats, liberals, leftists, and the rest to their bones, make little to no impression on conservatives because to them, such statements are mostly hyperbolic abstractions that don't sound like anything other than code for standing tall and being the best, greatest, amazing, winning country that the US should be but isn't.
This time, this one hits close to home because Trump's base, the GOP base, the common thread between the party and the campaign, has the one thing being taken advantage of in his comments.
Trump is talking about "doing what he wants" because he's "a star" to white women he comes across. the GOP/Trump base is composed almost exclusively of white men and white women. Trump can indeed get away with talking badly or violently about some abstract "other" especially since most of them are some shade of brown who are far away or at a minimum unfamiliar in their look or daily affairs as he imagines them. But every good Republican is or has personal contact with good old American white women every day, and talking badly about them is not acceptable.