MSNBC’s Mika Brzezinski brought her cat to the “Morning Joe” studios to mock J.D. Vance’s past comments about “childless cat ladies.” The Ohio senator and freshly minted Republican presidential nominee once dismissed Vice President Kamala Harris – now the likely Democratic presidential nominee — as a legitimate stakeholder in the nation she hopes to lead because, he argued, she did not have any children of her own and instead kept cats as pets. “We’re effectively run in this country via the Democrats, via our corporate oligarchs, by childless cat ladies who are miserable at their own lives and…