There was certainly a raging debate at the time about the correct way forward. Whether it did "buy future slaves their freedom" or not is debatable, too -- at least in the short-term. After being freed from slavery, most (or all? I'm not quite certain on this point) former slaves entered a period of "apprenticeship", which meant unpaid 45-hour working weeks for their former owners. In some ways their treatment in this period was even worse than their treatment as slaves. It did end, mercifully, in the late 1840s, but the sad fact is that it took a long time to go from the state of slavery to anything remotely resembling equal treatment.
I should go further, I guess, and say that it's our duty not just to ensure that it ever happens again but also to be honest about the scale of our historical involvement.