Trump's election showed that someone can say racist and other bigoted things and still be elected to the top position in the United States. This makes bigoted people more likely to be outspoken and active instead of keeping things quiet out of fear of being ridiculed. White supremacists, racists, and other bigoted groups feel much more safe now.
White supremacists believe that by Trump winning the presidential election, they will some how be more free to act on, and voice, their beliefs. White supremacists feel that President Elect Trump will support them, based off of his previous racial remarks, this will indeed lead to white supremacists being emboldened.
Donald Trump's campaign was built largely on xenophobia, racism and bigotry. White supremacists and the alt-right offered loud and vocal support to the president-elect throughout his campaign. Now that Mr. Trump has won the election, these people use his victory to proclaim that their views are popular with most of America. This emboldens them to be more outspoken and even physical.
These fringe people were not the people that voted Trump into office. He was not proud to have their vote. Trump knows the difference between securing the border and hate speech. In the end, these groups will not have an audience with any political power, and they will realize that they are not important.