It seems evident that no amount of argument will blunt your disregard for the feelings of outsiders who could not be expected to understand or appreciate the subtlties of your folk rituals. You can always find a perfectly valid reason to negate any objections. Here are a few more generalized examples that will, I hope, be less accusatory in nature and, thus, more condusive to discussion.
Rituals and rememberances are, often, retellings of epic or historical events and these events are, typically, military and heroic. Our histories are marked by conflicts, wars, conquests and defenses. Our enemies in these contests are demonized and their destruction is celebrated. These celebrations remain long after the specific events are forgotten, long after the animosities that that they commemorate are forgotten. So, "Rockaby Baby" has lost its political relevance even to those who are aware that it ever had any.
I have no idea where your blackface tradition was born or what it originally meant. Nor do I suggest that it is currently employed as a tool of racial disrespect. I can, however, offer a paralel that involves neither British custom nor Black/White relations.
This year, Mel Gibson released a filmed passion play depicting the death of Jesus. There was a hue and cry from the Jewish community protesting its release. Mr. Gibson and a sizable segment of the Christian world countered these protests with arguments not unlike yours. In a cacophony of accusation and reaction, including the possably irrelevant preachings of Mr. Gibson's father, the real reason for the protests were lost in the shouting. Here's the skinny.
Passion plays have been a staple in Europe for centuries. In fact, one town (I can't spell or pronounce its name)makes a decent percentage of their tourist income from their regular presentations.
I have no idea whether or not those townsfolk are anti-semitic. I do know that, in many countries, passion plays have been followed by pogroms perpetrated by inflamed, inspired peasants. Jews, who have been the victims of these atrocities, are more than a little aprehensive about their presentation. Let's face it, European Jews have an understandable edginess about some Christian traditions.
Can you doubt that Africans have similar wariness about White traditions?

          Mike