No, I'm not worried. This flag raising is very far from being Nazism and will blow over. However if the left keep calling everyone with a different view a fascist instead of taking on board other views or genuine concerns, divisions might increase.
I'm far more concerned about the hate I see on the far left. That is what is likely to drive me to leave the UK in the next few years and it says a lot when a Jewish person is far more afraid of the far left than the far right!
Nazism was far more than flag raising and Hitler youth camps. There was a sustained campaign of lies and rumours about Jewish people - who were very well integrated, and considered themselves Germans before anything - based purely on their ethnicity. Today that sustained campaign of lies comes from the left and Islamism. I see these lies every single day, along with now weekly physical attacks that are of no interest to mainstream media but if you follow Jewish news you are more aware.
While there are far right elements in British society I don't think we are in any danger of some kind of coup or serious riots. But people need to start remembering the ability to see other points of view and hear each other out without name calling, and since Brexit days, we seem, as a country, to have lost that ability Hostile elements (SWP, supporters of proscribed terror groups, Iran, Russia, far right) are able to stir things up purely because this division and name calling has become mainstream.