From the Columbia Guide to Standard American English:
"Democrat (adj., n.), Democratic (adj.):
The proper noun is the name of a member of a major American political party; the adjective Democratic is used in its official name, the Democratic party. Democrat as an adjective is still sometimes used by some twentieth-century Republicans as a campaign tool but was used with particular virulence by the late senator Joseph R. McCarthy of Wisconsin, a Republican who sought by repeatedly calling it the Democrat party to deny it any possible benefit of the suggestion that it might also be democratic."
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Stop trying to rationalize this as something other than a petty politcical tool.