Hidden agendas?

Tony Blair has expressed "deep sorrow" at Britain's role in the slave trade back in the 18th century. Quite right too, but this it would seem is not enough for some, who are demanding an apology. What's the difference? I think we're just playing with words here, and in particular asking Blair to do the impossible. He cannot truly apologise for something which was not of his own doing, and any suggestion that he should apologise on behalf of those involved in the slave trade back then would be an hypocrisy on their behalf because I am quite sure that those involved, if they were able to speak for themselves would see, by the standards of their time, nothing wrong in what they did, and that therefore they would have nothing to apologise for. I can't help but feel that those demanding an apology have their eyes more on the opportunity which that would open up for claims for some sort of compensation.