Letters to the Editor: mehadrin (separate) buses

The Mishpacha (Hebrew) magazine a couple of weeks ago ran a "Letter to the Editor" about the separate buses. This past week they ran another "Letter to the Editor" that was a response to the original. I do not have the original any longer, but the response quotes the relevant part of the original, so I will rely on that...

[the original letter is quoted]"On the way to a Haredi city, they requested from 4 grandmothers (they were not so old and infirm) to move out of the front sets of 8 seats. The young man asked politely and was holding a letter from the Rav of the town (a recommendation? a demand? a request?). Of course we did not refuse his polite request. Still, all my life I grew up with the concept that the front rows of seats on the bus are for the handicapped and/or older people. What will happen to [the mitzva of] Respecting the elders?"

[the response now begins]"I, reading this, want to note:
1. Why is it called a "polite" request and not a "just" request? Honored grandmothers, the ones that had enough energy and strength to walk to the bus-stop, to wait for the bus, to alight the bus, suddenly they have no more energy to take a few more steps further into the bus in order to avoid causing (even if only m'safek - even if only possibly avoiding) men to falter with an issur d'oraisa?
2. If they were grandmothers, how can they not be aware that not too many years ago smoking was allowed on buses by law and people smoked with no limitations. Yet today if anybody would dare smoke on the bus, and if people would "politely" request the person stop smoking, would the person write a letter to a respectable newspaper that he did no refuse a "polite" request even though he grew up and remembers a time when smoking on buses was permitted?
3. What about [the mitzva of] And you should be holy, that is written in the Torah?"

This letter leaves me without many words.
I am not sure what issur d'oraisa" the writer is referring to in point #1. Looking at women is an issur d'oraisa? it does not say it anywhere in the Torah. It might be a middas chassidus, but an issur d'oraisa? I doubt he can be referring to erva in general, because he does not say there were dressed improperly, or their hair was uncovered, which even then I am not so sure it is an issur d'oraisa.
If the men are concerned about issurei d'oraisa (that as far as I know do not exist), they do not have to look. That in no way obligates the women to move to the back of the bus.

I am not sure how he compares elderly in the front of the bus to smoking on a bus. Smoking has been declared illegal. Elderly sitting in the front of the bus is not illegal.

If you go to any parking lot or public place, the reserved seats or parking spaces for the handicapped and the elderly (when applicable) are always in the easy access areas and where it would be quicker for them to come and go (closer to the stores, near the aisles and/or front of a room), etc. It is basic humanity, aside from the mitzva of respecting the elderly, to be considerate of the elderly. Yet this fellow says "If they could walk this far, they can walk a little farther".