I am from a working class background, and in terms of racism, I think 'shunning' those who hold distasteful, prejudiced, derogatory etc views, does far more harm than good. What happens is they are pushed together, there is comraderie and unity in declaring 'immigrants take all our jobs' for example. Being shunned for these opinions reinforces them.
What is needed, I think, is to at least attempt to see where these views are coming from, and find 'gentler' ways of disproving them rather than just labelling them a racist bigot and shutting it down.
With specific reference to racism in feminism, I think it is often more nuanced than the typical anti immigrant type of racism most think of when they consider racism. I think it is more ingrained, and often not conscious racism if that makes sense. So you have white women championing anti FGM laws vehemently, who end up shutting out FGM survivors and taking over as it were, instead of pushing those survivors, people who come from a culture where FGM is practiced, because they inherently feel they know better, can campaign better, can explain it better.
To stamp that out is more difficult, and takes real soul searching from individuals.