The reason why I emphasize that is largely to rebut the premise that Dany is interfering with Ghiscari culture in an imperialist fashion – after all imperialism is not inconsistent with banning certain practices that might be considered immoral (hence Napier’s statement on sati, for example) – by pointing out that there is the culture of the slave (and in the case of slavery as practiced in Slaver’s Bay, there’s actually many cultures of slaves) and the culture of the slavemaster, so the situation is rather more complicated than a crude Orientalist analysis might suggest. (There’s also the fact that Dany actually shares a good bit of ethnic and cultural background with the Ghiscari…)
But to answer your question…as someone who’s argued the proper historical parallel for Dany’s narrative is the American Civil War and Reconstruction, there was a case where the slavemaster had largely (but not entirely) imposed their culture on their slaves. But in sharp contrast to “Lost Cause” narratives then and now about loyal slaves fighting for the Confederacy, despite their shared culture, African-Americans in the South didn’t share the belief that they should be slaves (and in the case of Nat Turner, we can see that shared culture being used to justify and motivate slave rebellions), and attempted to free themselves the moment that it was practical.
So if the Ghiscari slaves didn’t want to be slaves – and in Astapor, Yunkai, and Meereen, there were likely more than a few slaves of Ghiscari ethnicity, and they demonstrated their feelings on slavery quite clearly (if sometimes equivocally, as seen in ADWD) – then I don’t see Dany’s actions as imperialist in nature.