Story highlights Blackface is makeup worn by white theatrical performers to appear black.

It was common in the mid-19th century and into the early 20th century, but has since become regarded as perpetuating racist stereotypes.

(CNN) George Takei likely went where no critic of a Supreme Court justice has gone before.

But days after the "Star Trek" actor called Justice Clarence Thomas a "clown in blackface" following his dissent in last week's landmark same-sex marriage ruling, Takei said on Friday that his words "were not carefully considered."

"When asked by a reporter about the opinion, I was still seething, and I referred to him as a 'clown in blackface' to suggest that he had abdicated and abandoned his heritage," Takei said in a Facebook post. "This was not intended to be racist, but rather to evoke a history of racism in the theatrical arts. While I continue to disagree with Justice Thomas, the words I chose, said in the heat of anger, were not carefully considered."

The spat began after last week's historic same-sex marriage ruling, when Thomas, one of four justices to dissent, wrote that denying gays and lesbians the right to marry is not denying them of their dignity.

"Human dignity cannot be taken away by the government," wrote Thomas, who is black. "Slaves did not lose their dignity (any more than they lost their humanity) because the government allowed them to be enslaved. Those held in internment camps did not lose their dignity because the government confined them."

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