In certain cases good intentions indeed protect us from negative results of otherwise harmful actions, but such cases should not be extrapolated universally, since after all what makes samsara so dangerous is that good intentions are perfectly compatible with ignorance which is the most blameworthy quality. After all nobody will perform deliberately certain actions knowing that it will lead to his own suffering. But as we know from Suttas and from our own experience, people notoriously perform actions of very low quality.
“Bhikkhus, without having abandoned these five obstructions, hindrances, encumbrances of the mind, states that weaken wisdom, it is impossible that a bhikkhu, with his powerless and feeble wisdom, might know his own good, the good of others, or the good of both …AN V 51
So one may even argue that many times good intentions may be more harmful to us than ill will. And there is nothing paradoxical in such idea, in fact it should be quite obvious: as Dhamma followers who haven’t realised nibbana we are likely from time to time to be overcome by ill will and perform certain actions influenced by it. But since we practice Dhamma sooner or later we are able to see that we went wrong and so we will try to correct ourselves. But if our intentions are good and due to ignorance we do not see clearly all implications of our actions, we likely will continue to act in that way, quite satisfied with ourselves, hoping to receive merit from that line of action.
So coming back to question of wrong translations, I think there is distinction between translations of Suttas and teaching the Dhamma. Suttas are Buddha’s words, and as far as teaching about morality goes, things as they are, are stated quite unequivocally and it is really difficult to distort the meaning of the five precepts or for example descriptions of right speech. So it is simply impossible to not get merit by translating such Suttas. Perhaps due to such things as style or lack of accuracy (which however does not distort the meaning of the text), merit can be less substantial.
Unfortunately there are also Suttas which deal with right view, where the most subtle distortion of the meaning may be very important. But in such cases we have to take into account, that not so many people have potential to see Dhamma, so such subtle points which aren’t perceived by the translator, they are usually beyond of comprehension of the most readers, and so cannot be harmful to them. So only if certain particular translation really mislead one who otherwise was capable to see Dhamma, translator can expect some negative results. But it should be neutralised by merit from translating Suttas which do not deal with the right view. Also, in the present situation it should be obvious that even if certain translations are misleading it is very unlikely that they would mislead one who has potential to see the Dhamma. Such people by the very definition are intelligent enough to understand that there are not perfect translations, so being interested in Dhamma either they learn Pali, or at least compare many other translations. Anyway one cannot blame only the translator. Pali texts are available, so even if one is mislead, it is so because for this or that reason one didn’t boder to learn Pali.
Teaching of Dhamma seems to be much more dangerous activity, since unlike translations of Suttas, there are possibilities to teach things which in fact are in contradiction even with five precepts, not to mention more subtle points of Dhamma. And while some teachers may be overcome by “gain and honour” so in such cases we cannot speak about “good intentions”, some teachers may distort the meaning of Dhamma with perfectly good intentions since their main fault is that they overestimate themselves. And unfortunately is such cases negative results of their actions may indeed be harmful, the more influential and popular teacher is the greater his merits or demerits depends on quality of his teaching. After all Dhamma offers immortality, it is the highest offering, and responsiblity of one who distorts the meaning of Dhamma is greater than that of one who kills the body. Next birth is coming anyway, but next opportunity to meet and understand the Dhamma may not come so quickly…
“So too, bhikkhus, as to those recluses and brahmins who are unskilled in this world and the other world, unskilled in Māra’s realm and what is outside Māra’s realm, unskilled in the realm of Death and what is outside the realm of Death—it will lead to the harm and suffering for a long time of those who think they should listen to them and place faith in them. MN 34
“Bhikkhus, those bhikkhus who explain non-Dhamma as Dhamma are acting for the harm of many people, the unhappiness of many people, for the ruin, harm, and suffering of many people, of devas and human beings. These bhikkhus generate much demerit and cause this good Dhamma to disappear.
131 (34)–139
(131) “Bhikkhus, those bhikkhus who explain Dhamma as non-Dhamma … (132) … non-discipline as discipline62 … (133) … discipline as non-discipline … (134) … what has not been stated and uttered by the Tathāgata as having been stated and uttered by him … [19] (135) … what has been stated and uttered by the Tathāgata as not having been stated and uttered by him … (136) … what has not been practiced by the Tathāgata as having been practiced by him … (137) … what has been practiced by the Tathāgata as not having been practiced by him … (138) … what has not been prescribed by the Tathāgata as having been prescribed by him … (139) … what has been prescribed by the Tathāgata as not having been prescribed by him are acting for the harm of many people, for the unhappiness of many people, for the ruin, harm, and suffering of many people, of devas and human beings. These bhikkhus generate much demerit and cause this good Dhamma to disappear.”.
“Bhikkhus, those bhikkhus who explain non-Dhamma as non-Dhamma are acting for the welfare of many people, for the happiness of many people, for the good, welfare, and happiness of many people, of devas and human beings. These bhikkhus generate much merit and sustain this good Dhamma.” AN II