The documentary was already considered to be highly controversial at a time when white supremacist groups are gaining confidence and attacking ethnic minorities all over the United States. The documentary was perceived as giving these individuals a soapbox to share their political views and inviting sympathy for the members as individuals which was deemed highly inappropriate. The fact that they had been paid to contribute to the documentary was the final straw for many and it is right that the production company pulled back from broadcast.
A&E has strict rules about participants not receiving monies from outside or 'third-party' sources. When it came to light that the participants on its docu-series about KKK members, they had every legal right to cancel the series, after finding out that these policies were broken. By allowing it to continue, it would show that policies are not set in stone and would show a lack of integrity.
I was not aware there were pros and cons to free speech!! Alas, though, was this really free speech as producers of the show compensated the owners of what they said?
In any event, there are many shows less interesting than what this could possibly be. I would like the choice to either watch it or not.
Canceling a series on the KKK just because some of the participants were paid is unnecessary. They are not going to give the money back whether it is aired or not, so airing the series on the KKK is the better route. Exposing the KKK and its members is probably the best way to turn normal society off from them.