There is no unary definition of a "conservative". And certainly no definition which limits them to paragons without hate in their hearts. The most common kinds are social, religious, and fiscal conservatives and general reactionaries. There are also Constitutional conservatives, but they are a lot less common than they used to be. There are common combinations, like social and religious, social and fiscal, and anything and reactionaries. There are even some triples. But all can include haters. 
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In the end, we are left with "they are if they say they are." John Clarke says he is one, so we call him one. The nazis, KKK, etc. call themselves conservatives, so we call them conservatives. Just like when the KKK and the Westboro group call themselves Christians. 
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The old "they're not REAL C's" just doesn't cut it.