Society will always have its bad eggs, no matter their background/culture you will get people that do 'racist' things. Just as you will have rude, selfish, ignorant people that offend people other ways.
Society will never be perfect.
As someone said earlier, you can agree and disagree on politics - the latter shouldn't always be labelled as racist either.
Right now, the system is broken and there are frustrated people.. doesn't excuse a collection of them for the insults and way they express themselves.
It's quite simple... at a place game, if you see something, hear something that you disagree with, call it out. There's stewards and staff and other good supporters around you.. that will stamp it out.
So to summarize.. there are indeed bad people that will display racist behaviour.. call it out at the time, report them.. that will do the job..
But I gotta say, palace fans in my opinion are the least racist and indeed the most welcoming fans I have known... you just have to look at where it's based and the star players we have had for decades...