It would've been such, had he killed they guy for spite, but he actually used it as a way to get back into Thack's (and every other folk there) grace, while simultaneously kicking down Edwards.
So it makes logical sense for the character, rather than just trying to make him do the worst possible thing at every turn.
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I'll say, i like how the show isn't too concerned about making characters likeable, and instead decides to stick to the tone of the times.
An example of them, is not only not having him perplexed or repulsed, but showing Thack and Abigail outright laughing and enjoying the cringeworthy blackface comedians.
Honestly, a lesser show would've taken that opportunity to have Thackery say something anachronistically progressive, just for fear of having him show unlikable sides.
This was doubly true in S1, when he was even more outright racist in Edwards' regards.