@Deanna142 As you can see from the responses here, others feel that the way this host tried to get his message across was a poor approach-I think many guests would react like you did. But as you can also see, we do sympathise and understand where he is coming from in being afraid of having his ratings tanked, because of how harshly Airbnb applies the ratings to hosts, which most guests are completely unaware of.
Airbnb tells guests on the review form that 4*s is a good rating, then they turn around and threaten hosts with delisting when their rating falls below 4.7. It's an extremely frustrating and irritating situation that they mislead guests and punish hosts- and, as you say, if 5*s is the norm not to get threatening messages from Airbnb, it makes the star ratings not believable. In a sane world, there should be nothing whatsoever wrong with something being rated 4*s and considered "Good".
Some of my guests who are aware of how harshly the ratings can affect hosts have told me that if the place is basically fine, and the host is nice and attentive, that they rate 5*s and mention anything they feel could be improved to the host in private feedback. You can also rate 5*, but mention something you feel needs improvement in the written review, to let other guests know.
Of course there are places that definitely don't deserve 5*s, no matter what, places that are dirty, that have broken appliances or fail to have the amenities listed, or ones where the host doesn't address legitimate guest issues raised during the stay.
You say you've had a lot of stays on Airbnb, so I'm a little surprised you weren't aware that hosts' and guests' phone numbers are visible to each other after a booking is confirmed.
I wouldn't worry about a bad review- if I were in your shoes, I would tell the host that you had every intention of rating him 5*s, but that his approach in messaging you about the star ratings is very off-putting, and that he might want to rethink sending such a message to guests again.
It's quite true that if everyone is pressured to leave 5* ratings, that makes the ratings unbelievable. But if I were a guest, I'd not find star ratings to be valuable to me in making a decision anyway, as they are so subjective- what might be a wonderful 5* location to you, might be an inconvenient, less than desirable location to another, so it's what people actually write that I'd go by. Same with ratings of guests- I'd take them with a grain of salt- what another host might have found annoying about a guest might be something that wouldn't bother me at all.