The problem with the 'it's all a massive trolling of the American people by Trump' meme is that Trump's followers are not trolling.
The problem isn't whether or not, however, if they are serious or not. The problem would exist if they possessed the actual ability and approval
of society to act on their particular set of beliefs. I can believe that the Earth is flat all that I want to, but I'm just a crazy man screaming nonsense in a corner without any way to actually enforce my views on people. And I say enforce quite literally because there is less than 0% chance of me actually convincing someone through evidence that the world is flat.
That said, if Trump would actually give people like what you describe a pathway to force their beliefs on the rest of America, then there exists a problem.
If there's one thing Trump has done that is good, it has silenced the talking heads who say that racism is dead in America. It's been more like kicking a rotten log and seeing all the vermin spill out.
Of course racism isn't dead. As long as there are races, distinct in their ethnic identity, there will be racism. The total elimination of racism is not an ideal goal for a liberal, democratic society because of the necessary policies that would need to be put into place. The goal should be that institutional racism, racism enforced at the end of a gun or laws or whatever - stuff like Jim Crow - should be eliminated, and that racist ideology should be exposed for the brand of ignorance that it is and shunned on a widespread societal basis. Goals that have largely been achieved. The Fox News cry of 'racism is dead b/c we have a black President' is simply something they use to further their political narrative, having no more substance in fact than the idea that the Earth is flat.
16% of them think getting rid of slavery was a bad thing. 31% are either sure or not certain if whites are a superior race. That shouldn't take too many brain cells to decide on.
In the one case, that is not precisely a great number of people, in the latter...more to come.
Let's say that Trump wins with 50.5% of the vote. If 16% of his supporters believe that getting rid of slavery was bad, then that means that about 8.1% of the US population believes it, for a total of about 26 million people...a number slightly higher than the population of North Korea (24 million). This is, of course, almost certainly not true, considering that not every person voting Trump would do so because they wholeheartedly support him. And that number, I would guess, would be concentrated in certain areas of the country.
The latter is...it can be hard for some people - especially dumb ones - to separate superior race
from superior culture
. I may just be thinking naively, but I'm guessing that most of those people aren't saying white people are racially superior, they're culturally superior. Which is a thing. Not that white culture is superior to black culture, but that you have certain cultures that are superior to others in general. Nobody would say that the culture of 8th century France is just as good as the culture of France today.
Racial superiority - in the strictest sense - is difficult to measure. Race is basically based upon genetic patterns and selections. How do you measure the superiority of one set of genes to another?