If "liberty" means freedom and "justice" means fairness and equity, then why do conservatives have a problem?

Since when do we give rights to change the definition of words. Marriage has always been defined as between a man and a woman. Anyone is free to marry a person of the opposite , the only exception is you can't marry a close relative. Same marriage is a misnomer, since by definition marriage is not same . Same union, partnership, etc would be Ok. To liberals, words/promises don't seem to matter.