Who said anything about them taking the slaves to any British Colonies? As that quote mentioned, they sold them to Spanish slave drivers in the New World, having captured them in Africa. A profitable business transaction, and they were first and foremost business men. Entrepreneurs/pirates/merchant adventurers.

Here's a BBC page about Hawkins and the slave trade. It's not exactly a new or secret revelation, it just something that tends to be passed over in popular accounts of the Elizabethan seafarers. (And here is a story form the Times earlier this year about one of Hawkins' descendants on a trip to West Africa - Slaver's descendant begs forgiveness

It's not a question of me wanting it to have happened. It happened. Nothing personal about it. And I'm not implying that Hawkins and co were uniquely responsible. The slavers were English, Dutch, Spanish, Portuguese, Arab...

I'd much prefer it hadn't happened, that the whole slave trade had never happened. Not just because of the suffering at the time, but also because of the consequences we are still living with. (All right without the African American presence America and the world would be culturally much poorer, but the devastation to Africa has to outweigh that.)

And I quite agree that one of the corollaries of denouncing the past horrors of slavery should be a genuine determination to bring an end to the present day versions of slavery.