Many imigrants come from countries where holidays, spare time and leisure activities does not exist. They work to feed themselves and their families, in feudal societies, and the concept of going fishing just for the fun of it, is utterly ridiculous. The sort of coarsefishing tradition that exists in the UK, is the result of a long historic journey, starting with the with the aristocrasy, with plenty of time to pursue whatever they wanted. The industrial revolution created a large upperclass of industrialists and bankers, with time off and with money to spend. Who did what it took to resemble the nobles as best they could. And eventually, through unions and class struggle, a working class who could afford to buy gear, and had time off to go fishing.
None of these things happend in most of the countries the asian or african immigrants left. It's starting to happen now. When they are producing everything we consume. That will eventually leave them rich, and us poor. At least most of us.
When it comes to hostile remarks and comments at the bankside, that has to do with common decency. Or the lack of it. There has always been, and will always be, people who, for various reasons, don't know how to behave. Maybe some are racist, maybe some are just stupid. But angling as such is not racist. It's not antiracist either. It cannot be. It's just a way to spend your time.