I disagree with your opinion, but I'll defend your right to express it to the very end.
Literal
I [topic-は] you [possessive-の] opinion [to-に] disagreement [but-だが] it [object-を] state you [possessive-の] right [topic-は] end [until-まで] will-protect.
A Japanese rendering of the sentiment attributed to Voltaire. 不賛成 ('disagreement') — the negative prefix 不 + 賛成. 述べる (のべる, 'to state, express') is formal/literary. 権利 (けんり, 'right'). 護る (まもる, 'to protect') — the kanji 護 is more formal than the common 守る. ~てやろう uses the volitional of ~てやる ('do for someone,' from a position of initiative).