Answer

Hello Rabbi Y.,
1. I read it. I assume that Rabbi Lichtenstein here is following his father-in-law’s approach regarding the presumption that “it is better to dwell as two,” who wrote that presumptions were given at Sinai and are eternal. In my view, it is unlikely that he himself really believed this, and he probably wrote it as a response to the heretics. Rabbi Lichtenstein certainly knew very well about the influence of changing reality and renewed values on Jewish law, and he probably was also concerned about a Reform-style slippery slope.
2. Still, one must distinguish sharply between this and the attitude toward the deaf and hearing-impaired. There Maimonides already writes in his commentary to the Mishnah that this is not an essential problem but only an inability to learn, and once that is resolved there is no obstacle to changing the Jewish law on this matter. Therefore Rabbi Benny’s example is not a good one.
3. Even so, of course, it would be preferable to prove from the sources that the issue really is that a priest with a physical defect is regarded as something inferior (“offer it, please, to your governor”), and then there would be room for the claim that today this has changed.
4. By the way, the argument in section 3 is different from Rabbi Benny’s argument. As I understand it, he argued that today’s norms require changing the attitude toward people with physical defects because there is an obligation to draw them near and because equality is a value. In response to that, I can understand Rabbi Lichtenstein’s outrage, since he rejected the possibility that the Sages behaved immorally toward people with physical defects, though I am really not sure he was right. That is a value-change that affects Jewish law, and that is what Rabbi Lichtenstein opposed. But in my opinion it should be phrased a bit differently: the change is factual, not value-based, and then it becomes an entirely legitimate halakhic argument. Today’s norms have caused a person with a physical defect not to be regarded as something inferior, and therefore Jewish law itself does not disqualify him, because today he does in fact meet the criterion of “offer it, please, to your governor.” That is a completely different formulation from the first one, despite the apparent similarity. Here the claim is that Jewish law itself requires a change in application because circumstances have changed, whereas Rabbi Benny’s claim is that Jewish law disqualifies a priest with a physical defect, but contemporary moral values prevent us from acting that way. That really does smell like Reform and lack of commitment to Jewish law, but rather commitment to the values of the age. (By the way, even that is not categorically invalid. See the fifth part of the Shulchan Arukh, but this is not the place to elaborate.)
 
5. I am sending two articles, one dealing with converts and the other with changes in Jewish law in general:
 
https://mikyab.net/%D7%9B%D7%AA%D7%91%D7%99%D7%9D/%D7%9E%D7%90%D7%9E%D7%A8%D7%99%D7%9D/%D7%94%D7%9E%D7%A2%D7%9E%D7%93-%D7%94%D7%90%D7%99%D7%A9%D7%99-%D7%A9%D7%9C-%D7%92%D7%A8-%D7%90%D7%A4%D7%9C%D7%99%D7%99%D7%94-%D7%90%D7%95-%D7%A1%D7%98%D7%98%D7%95%D7%A1-%D7%97%D7%91%D7%A8%D7%AA%D7%99/
 
https://mikyab.net/%D7%9B%D7%AA%D7%91%D7%99%D7%9D/%D7%9E%D7%90%D7%9E%D7%A8%D7%99%D7%9D/%D7%94%D7%90%D7%9D-%D7%99%D7%A9-%D7%A2%D7%91%D7%95%D7%93%D7%94-%D7%96%D7%A8%D7%94-%D7%A0%D7%90%D7%95%D7%A8%D7%94-%D7%A2%D7%9C-%D7%94%D7%99%D7%97%D7%A1-%D7%9C%D7%92%D7%95%D7%99%D7%99%D7%9D-%D7%95/
 
6. As for the blind person, I did not understand the question. Do you mean the obligation of a blind person in the commandments? Here too all the above types of arguments have to be considered.
By the way, also regarding desecrating the Sabbath in order to save an eye, in the case of eye ailments one has to discuss this carefully: why is danger to an eye considered a life-threatening situation? As is known, Rashi and his grandson Rabbenu Tam disagreed on this (Avodah Zarah 28b): one of them explains it medically (danger to the eye can endanger life), and the other explains it essentially (loss of an eye is considered like loss of life). Both of these rationales deserve reexamination in light of present-day reality and, of course, current medical knowledge.