Would you accept the apology from the bloke that called dabo the names?
I might regret this...
But, you know those footballers, cricketers etc who get pulled up for racist, homophobic tweets etc they sent in the past? If they apologise and make clear they're against racism / homophobia / whatever then yes, it's probably worthwhile giving them the benefit of the doubt. If you said something to offend me, personally, and you apologised for it then yes, I would accept it... My general philosophy is we will all say things that offend somebody, it's how we respond to that, that matters. If it's a fuck you, it's my right to say that don't be such a snowflake then it's no holds barred in response. If, however, it's a recognition of offence and an attempt to change behaviours, then that's righting a wrong.
Now, apologies if this comes out wrong but...
Might it not be a good idea to start a thread in off-topic about the kind of regular discrimination your neice gets, and how it affects her, her family... you? It would be useful to draw attention to that, wouldn't it? Make us all think about what we say, and do? As it stands, all that happens is you're maybe not being able to get people to see what she has to put up with, and also it ends up derailing a point where we should all be agreeing that racism is bad, yes?
Doesn't your neice's discrimination deserve its own space, rather than as an adjunct to something else?