Nope, its not an insult. I use Black British for myself (born and bred Londoner!) and Afro-Caribbean for folks from my heritage not born in the UK.
Londoners represent! Ahem.
This is one of those things where American issues get conflated across the world. Racism is racism...well for the most part, the word gets used a lot sometimes. America has very specific things in its history..slavery on the mainland, being a young nation of mostly immigrant people, its history with Native Americans, difficulties between different groups of settlers, but most importantly the need for the civil rights movement in the mid twentieth century and the things like government enforced segregation and even having slavery in its laws until ridiculously recently. The UK has different problems, and that makes our perspective different (and us Londoners, especially us working class people) to what you get in America. Plymouth Rock didn't land on anyone here. A bunch of people did have to deal with some nasty stuff, for a long time, (will it ever end? I cannot describe my anger at finding out things I thought long gone were back after recent events.) The more globalisation conflates the two cultures though, the more things get dicey (look at poor old Benedict Cumberbatch recently) and you get weird things happen.
It's even more specific than that it turns out...us Londoners, particularly of a certain generation, (because I think sadly the world has gone backwards of late in that area, and because the Brexit and stuff that has followed shows that outside of London things are a bit different again...man, the anecdotes I could tell you.) make the federation look segregated in comparison. It's one of things that makes me consider the globalisation of culture a bad thing, because making assumptions gets people caught in all kinds of misunderstandings, and is working against everyone.
A fair chunk of my mates growing up are Afro Caribbean, couple of Africans, Chinese via HK...Irish...Indian (and that general region) ....but we were all Brits, all Londoners, and frankly didn't give a monkeys about all that beyond the odd amusement at differences that mainly existed between our parents and not us. The difference between us, and particularly the Afro Caribbean and the British, was fag paper thin. Like one or two family favourite dishes and where we go on our holidays thin ( and let's be honest, we all went to Spain if we were lucky, but more likely Southend etc.)
One of the things I like about Trek is it reminds me a bit of those days (we seem to have got more segregated and gentrified and ghettoised here in the last twenty or so years.) particularly with stuff like Bashir and O'Brien. Sisko really should have joined them in the bar more often.
It bothers me that there are deep discussions about who should be represented in Trek, and further outside, that we seem to have to get caught up in this identity struggles more than at any time....just as we thought we were moving out of such tribal nonsense.
Then I go and listen to some house, maybe some old school drum and bass, and text my oldest best mate, if he's not at a folk festival or a beer festival, and remember if people like us still exist, maybe I shouldn't give up hope just yet.
Just like Star Trek init.