I was reading the thread waiting for someone to say "wah but racism has to be systemic and institutional and widespread to really be racism, if it's just against one person it's discrimination not racism".
This is the idea that the woke brigade have been pushing recently, and unsurprisingly it's taken off more in the US and lots of British consumers of US social media and so forth are trying to apply the same thing in the UK. But it goes against the simple definition of the word and convolutes the issue for seemingly no reason.
Dictionary definition of racism:
1 The unfair treatment of people who belong to a different race; violent behaviour towards them
2 Prejudice, discrimination, or antagonism directed against a person or people on the basis of their membership in a particular racial or ethnic group
3 The belief that some races of people are better than others
And so on. There is no major dictionary that states it has to be systemic and historic for it to be racist.
So yes, based on the dictionary definition rather than the tumblr argument, white people can experience racism. I experienced it a LOT from the south asian community when I was in a relationship with an Indian man in my early 20s.