Apparently only conservatives and others on the right can be obstructionists, according to Roget’s Thesaurus.
A search for synonyms of “obstructionist” on Thesaurus.com, which cites Roget’s, reveals that the source considers several words related to conservative and right-leaning political stances to fit the definition of a “person who is cautious, moderate; an opponent of change.” Under antonyms, it lists left-leaning words.
Other synonyms listed for obscrutionst are “traditionalist,” “conserver,” “conventionalist,” “unprogressive,” and “redneck.”
This is the second time in recent weeks that a reference book has equated a negative quality with conservatism. Earlier this month, the Daily Caller found that both the Oxford English and Merriam-Webster dictionaries included “right-wing” and “conservatism,” respectively, in their definitions of “bigotry.”