Whether Colonel Sanders killed a man years ago is not relevant to eating at KFC today. Besides, it is a myth that Colonel Sanders killed anyone in the first place. There is no benefit to knowing the information about this myth unless you're on a game show about urban legends.
The character that is KFC's Colonel Sanders has become separated from the man who really lived. And morality of a different time and place really shouldn't be the basis of decided where one gets fried food. The other chicken restaurant has said and done things far more offensive in the present day.
The incident in question happened in 1930, so while it's an interesting story, it should affect the business now. Sanders himself has been dead since 1980, and the current employees and executives involved with the company had nothing to do with what happened. What people should focus on now, for this business or any other one, is whether or not their current practices are fair and ethical, not on incidents from decades ago that have little to no bearing on today.
Just pass some of that original spices chicken with the mashed potatoes and coleslaw. Colonel Sanders is just a figurehead. No one cares about his escapades. As a matter of fact throw in a cherry coke and I'm all set. I'll be driving away, burping in bliss once I consume my meal.