@Tuhin3 It's understandable that you are choosing not to take this high-risk trip with your child, and I think in that sense you made the best choice. Once again, I would encourage you to take this up with your insurance - which is quite an essential thing to have when you stand to suffer a heavy loss when unforeseen conditions affect your trip.
Where we might disagree on the ethics is the notion that your host (or Airbnb itself) should act guests' de facto insurer when they don't choose to insure their trips. The host's ethical obligations are to honor the terms of your booking agreement, for the specific dates of your stay and number of people in your group, and deliver the home exactly as advertised. In the event of cancellation, they're obliged to honor the terms of the cancellation policy you agreed to - noting that you could have chosen a listing with a more flexible policy if you preferred to have that option. The host is never required by law, nor by ethics, to grant an opportunity to reschedule or offer the same rates for different calendar dates. That would constitute a change to the contract, when is only valid if both parties willfully agree to it.
I don't know how things went down in your correspondence with this host, but clearly they don't feel that this bird in the hand is worth two in the bush - to the extent that they would even sacrifice other potential bookings to avoid hosting you. They are not exactly wrong to feel this way, considering that you are publicly defaming them on a highly visible website. Once a host gets a whiff of vindictive behavior in their guests, they would be very wise to prevent those guests from re-booking or re-scheduling rather than risk damage to their homes or reputations.
