It is not a half thruth at all. It is entirely wrong that we traded in African people. There are no buts needed.
Absolutely it is. Even the "couple of generations" of slave keeping and slave trading mentioned represents incalculable human suffering and trauma. There's a lot there to study.
But you can't call slave trading, though, is "white behaviour", as it wasn't practised by most white people, not all the people who practised it were white, white people haven't persisted in the behaviour. "White behaviour" doesn't doesn't make sense as a label for it.
What you can say, for example, is that colonialism was a big trend for most European nations for about three hundred years. So if you want to identify bad behaviour from western civilisations at great cost to other non-European societies, it's very easy to do.
Which makes this unexplained determination to shoe horn the word "white" in somewhere whether it makes sense or not even stranger.
You know people's actions aren't determined by their skin colour, don't you? Politics and culture and societal norms are what influence behaviour, and even then, people from the same time and place behave very differently from one another.