The sentence contrasts initial reluctance to judge with firm commitment once a decision is made. Intransigent means refusing to change one's position — perfectly describing someone who, once decided, won't back down. 'Resolute' is the synonym pair in the original. 'Deferential' means yielding to others — opposite of holding firm. 'Lax' and 'negligent' both imply carelessness, contradicting the idea of vigorous defense.