I think it is important. It gives the character moral honor. I do believe also that it should occur within a.action event. Such as uncovering a ranch where illegal slavery is being conducted.
I take it the time event is "modern". You could have the ranch being run by a high authority in government who is using children that are not being allowed entry into the USA working on his farms.
Then you can introduce why, in the past, he is so adverse to slavery (maybe with a flashback) and his current action to rectify this occurrence.
Of course, now this becomes a minor event in the book, but it should!